Resist composition and method of forming resist pattern

ABSTRACT

A method of forming a resist pattern, including: step (1) in which a resist composition containing a base component (A) that exhibits increased solubility in an alkali developing solution and a compound represented by general formula (C1) is applied to a substrate to form a resist film, step (2) in which the resist film is subjected to exposure, step (3) in which baking is conducted after step (2), and step (4) in which the resist film is subjected to an alkali development, thereby forming a negative-tone resist pattern; and the resist composition used in step (1): 
     
       
         
         
             
             
         
       
     
     wherein R 1  represents a group which forms an aromatic ring together with the two carbon atoms bonded to the R 1  group; R 2  represents a hydrogen atom or a hydrocarbon group; and R 3  represents a hydrogen atom, a carboxy group or a hydrocarbon group of 1 to 15 carbon atoms.

TECHNICAL FIELD

The present invention relates to a method of forming a resist pattern inwhich a negative-tone resist pattern is formed by developing with analkali developing solution, and a resist composition for use in suchmethod.

Priority is claimed on Japanese Patent Application No. 2012-003412,filed on Jan. 11, 2012, the content of which is incorporated herein byreference.

BACKGROUND ART

Techniques (pattern-forming techniques) in which a fine pattern isformed on top of a substrate, and a lower layer beneath that pattern isthen fabricated by conducting etching with this pattern as a mask arewidely used in the production of semiconductor devices and liquiddisplay device. These types of fine patterns are usually formed from anorganic material, and are formed, for example, using a lithographymethod or a nanoimprint method or the like. In lithography techniques,for example, a resist film composed of a resist material containing abase component such as a resin is formed on a support such as asubstrate, and the resist film is subjected to selective exposure ofradial rays such as light or electron beam, followed by development,thereby forming a resist pattern having a predetermined shape on theresist film. Using this resist pattern as a mask, a semiconductor or thelike is produced by conducting a step in which the substrate isprocessed by etching.

The aforementioned resist material can be classified into positive typesand negative types. Resist materials in which the exposed portionsexhibit increased solubility in a developing solution is called apositive type, and a resist material in which the exposed portionsexhibit decreased solubility in a developing solution is called anegative type.

In general, an aqueous alkali solution (alkali developing solution) suchas an aqueous solution of tetramethylammonium hydroxide (TMAH) is usedas the developing solution. Alternatively, organic solvents such asaromatic solvents, aliphatic hydrocarbon solvents, ether solvents,ketone solvents, ester solvents, amide solvents and alcohol solvents areused as the developing solution (for example, see Patent Documents 1 and2).

In recent years, advances in lithography techniques have lead to rapidprogress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength (increasing the energy) of the exposure light source.Conventionally, ultraviolet radiation typified by g-line and i-lineradiation has been used, but nowadays KrF excimer lasers and ArF excimerlasers are starting to be introduced in mass production. Furthermore,research is also being conducted into lithography techniques that use anexposure light source having a wavelength shorter (energy higher) thanthese excimer lasers, such as electron beam (EB), extreme ultravioletradiation (EUV), and X ray.

As shortening the wavelength of the exposure light source progresses, itis required to improve various lithography properties of the resistmaterial, such as the sensitivity to the exposure light source and aresolution capable of reproducing patterns of minute dimensions. Asresist materials which satisfy such requirements, chemically amplifiedresists are known.

As a chemically amplified composition, a composition including a basematerial component that exhibits a changed solubility in a developingsolution under the action of acid and an acid-generator component thatgenerates acid upon exposure is generally used. For example, in the casewhere an alkali developing solution is used as a developing solution(alkali developing process), a base component which exhibits increasedsolubility in an alkali developing solution under action of acid isused.

Conventionally, a resin (base resin) is typically used as the basecomponent of a chemically amplified resist composition. Resins thatcontain structural units derived from (meth)acrylate esters within themain chain (acrylic resins) are the mainstream as base resins forchemically amplified resist compositions that use ArF excimer laserlithography, as they exhibit excellent transparency in the vicinity of193 nm.

Here, the term “(meth)acrylic acid” is a generic term that includeseither or both of acrylic acid having a hydrogen atom bonded to theα-position and methacrylic acid having a methyl group bonded to theα-position. The term “(meth)acrylate ester” is a generic term thatincludes either or both of the acrylate ester having a hydrogen atombonded to the α-position and the methacrylate ester having a methylgroup bonded to the α-position. The term “(meth)acrylate” is a genericterm that includes either or both of the acrylate having a hydrogen atombonded to the α-position and the methacrylate having a methyl groupbonded to the α-position.

In general, the base resin contains a plurality of structural units forimproving lithography properties and the like. For example, a structuralunit having a lactone structure and a structural unit having a polargroup such as a hydroxy group are used, as well as a structural unithaving an acid decomposable group which is decomposed by the action ofan acid generated from the acid generator to form an alkali solublegroup (for example, see Patent Document 3). When the base resin is anacrylic resin, as the acid decomposable group, in general, resins inwhich the carboxy group of (meth)acrylic acid or the like is protectedwith an acid dissociable group such as a tertiary alkyl group or anacetal group are used.

As a technique for further improving the resolution, a lithographymethod called liquid immersion lithography (hereafter, frequentlyreferred to as “immersion exposure”) is known in which exposure(immersion exposure) is conducted in a state where the region betweenthe lens and the resist layer formed on a wafer is filled with a solvent(a immersion medium) that has a larger refractive index than therefractive index of air (see for example, Non-Patent Document 1).

According to this type of immersion exposure, it is considered thathigher resolutions equivalent to those obtained using a shorterwavelength light source or a larger NA lens can be obtained using thesame exposure light source wavelength, with no lowering of the depth offocus. Furthermore, immersion exposure can be conducted by applying aconventional exposure apparatus. As a result, it is expected thatimmersion exposure will enable the formation of resist patterns ofhigher resolution and superior depth of focus at lower costs.Accordingly, in the production of semiconductor devices, which requiresenormous capital investment, immersion exposure is attractingconsiderable attention as a method that offers significant potential tothe semiconductor industry, both in terms of cost and in terms oflithography properties such as resolution.

Immersion lithography is effective in forming patterns having variousshapes. Further, immersion exposure is expected to be capable of beingused in combination with currently studied super-resolution techniques,such as phase shift method and modified illumination method. Currently,as the immersion exposure technique, technique using an ArF excimerlaser as an exposure source is being actively studied. Further, water ismainly used as the immersion medium.

As a lithography technique which has been recently proposed, a doublepatterning method is known in which patterning is conducted two or moretimes to form a resist pattern (for example, see Non-Patent Documents 2and 3). There are several different types of double patterning process,for example, (1) a method in which a lithography step (from applicationof resist compositions to exposure and developing) and an etching stepare performed twice or more to form a pattern and (2) a method in whichthe lithography step is successively performed twice or more. Accordingto the double patterning method, a resist pattern with a higher level ofresolution can be formed, as compared to the case where a resist patternis formed by a single lithography step (namely, a single patterningprocess), even when a light source with the same exposure wavelength isused, or even when the same resist composition is used. Furthermore,double patterning process can be conducted using a conventional exposureapparatus.

Moreover, a double exposure process has also been proposed in which aresist film is formed, and the resist film is subjected to exposuretwice or more, followed by development to form a resist pattern (forexample, see Patent Document 4). Like the double patterning processdescribed above, this type of double exposure process is also capable offorming a resist pattern with a high level of resolution, and also hasan advantage in that fewer number of steps is required than theabove-mentioned double patterning process.

In a positive tone development process using a positive type, chemicallyamplified resist composition (i.e., a chemically amplified resistcomposition which exhibits increased alkali solubility in an alkalideveloping solution upon exposure) in combination with an alkalideveloping solution, as described above, the exposed portions of theresist film are dissolved and removed by an alkali developing solutionto thereby form a resist pattern. The positive tone process using acombination of a positive chemically amplified resist composition and analkali developing solution is advantageous over a negative tonedevelopment process in which a negative type, chemically amplifiedresist composition is used in combination with an alkali developingsolution in that the structure of the photomask can be simplified, asatisfactory contrast for forming an image can be reliably obtained, andthe characteristics of the formed resist pattern are excellent. Forthese reasons, currently, positive-tone development process using acombination of a positive chemically amplified resist composition and analkali developing solution is mainly employed in the formation of anextremely fine resist pattern.

DOCUMENTS OF RELATED ART Patent Document

-   [Patent Document 1] Japanese Unexamined Patent Application, First    Publication No. Hei 6-194847-   [Patent Document 2] Japanese Unexamined Patent Application, First    Publication No. 2009-025723-   [Patent Document 3] Japanese Unexamined Patent Application, First    Publication No. 2003-241385-   [Patent Document 4] Japanese Unexamined Patent Application, First    Publication No. 2010-040849

Non-Patent Documents

-   [Non-Patent Document 1] Proceedings of SPIE (U.S.), vol. 5754, pp.    119-128 (2005)-   [Non-Patent Document 2] Proceedings of SPIE (U.S.), vol. 5256, pp.    985-994 (2003)-   [Non-Patent Document 3] Proceedings of SPIE (U.S.), vol. 615301-1-19    (2006)

SUMMARY OF THE INVENTION

However, as further progress is made in lithography techniques and theapplication field for lithography techniques expand, further improvementin various lithography properties is demanded in a positive-tonedeveloping process using a combination of a positive chemicallyamplified resist composition and an alkali developing solution.

For example, in the formation of an extremely small pattern (such as anisolated trench pattern, an extremely small, dense contact hole pattern,or the like), a region where the optical strength becomes weak is likelyto be generated especially in the film thickness direction, therebydeteriorating the resolution of the resist pattern and the shape of thepattern.

In the formation of the aforementioned extremely small pattern, a methodof forming a resist pattern (negative pattern) in which regions wherethe optical strength becomes weak are selectively dissolved and removedis useful. For forming a negative pattern with a chemically amplifiedresist composition used in a positive-tone developing process which isthe mainstream, a method in which a developing solution containing anorganic solvent (organic developing solution) is used in combinationwith a chemically amplified resist composition is known. However,negative-tone developing process is inferior to a positive-tonedeveloping process using an alkali developing solution in combinationwith a chemically amplified resist composition in terms of environment,apparatus and cost. Thus, a novel method of forming a resist pattern hasbeen demanded which is capable of forming a negative-tone pattern with ahigh resolution and an excellent shape.

The present invention takes the above circumstances into consideration,with an object of providing a method of forming a resist pattern whichenables formation of a negative-tone resist pattern with a highresolution and an excellent shape, and a resist composition for use insuch method.

As a result of intensive studies, the present inventors have invented amethod of forming a negative pattern in which a resist film formed by aresist composition containing a base component that exhibits increasedsolubility in an alkali developing solution by the action of an acid anda photobase generator that generates base upon exposure has the exposedportions remaining and the unexposed portions dissolved and removed byan “alkali developing solution” (Japanese Unexamined Patent Application,First Publication No. 2011-106577). As a result of further studies ofthe present inventors, it has been found that, by shortening thediffusion length of the base generated at exposed portions of the resistfilm, a negative resist pattern with an excellent dimension uniformitycan be formed. The present invention has been completed based on thisfinding.

The resist composition of the present invention includes a basecomponent (A) that exhibits increased solubility in an alkali developingsolution and a photobase generator component (C) that generates baseupon exposure, the resist composition being used in a method of forminga resist pattern including: a step (1) in which the resist compositionis applied to a substrate to form a resist film; a step (2) in which theresist film is subjected to exposure; a step (3) in which baking isconducted after the step (2), such that, at an exposed portion of theresist film, the base generated from the photobase generator component(C) upon the exposure and an acid provided to the resist film in advanceare neutralized, and at an unexposed portion of the resist film, thesolubility of the base component (A) in an alkali developing solution isincreased by the action of the acid provided to the resist film inadvance; and a step (4) in which the resist film is subjected to analkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved, wherein the photobase generator component (C) contains acompound represented by general formula (C1) shown below.

In formula (C1), R¹ represents a group which forms an aromatic ringtogether with the two carbon atoms bonded to the R¹ group, provided thatthe aromatic ring may have a nitro group or a substituent other than thenitro group bonded to the aromatic ring; R² represents a hydrogen atomor a hydrocarbon group which may have a substituent; and R³ represents ahydrogen atom, a carboxy group or a hydrocarbon group of 1 to 15 carbonatoms which may have a substituent, provided that part of the carbonatoms constituting the hydrocarbon group for R³ may be replaced with ahetero atom.

Further, the method of forming a resist pattern according to the presentinvention includes: a step (1) in which a resist composition including abase component (A) that exhibits increased solubility in an alkalideveloping solution and a photobase generator component (C) thatgenerates a base upon exposure and contains a compound represented bygeneral formula (C1) shown below is applied to a substrate to form aresist film; a step (2) in which the resist film is subjected toexposure; a step (3) in which baking is conducted after the step (2),such that, at an exposed portion of the resist film, the base generatedfrom the photobase generator component (C) upon the exposure and an acidprovided to the resist film in advance are neutralized, and at anunexposed portion of the resist film, the solubility of the basecomponent (A) in an alkali developing solution is increased by theaction of the acid provided to the resist film in advance; and a step(4) in which the resist film is subjected to an alkali development,thereby forming a negative-tone resist pattern in which the unexposedportion of the resist film has been dissolved and removed.

In formula (C1), R¹ represents a group which forms an aromatic ringtogether with the two carbon atoms bonded to the R¹ group, provided thatthe aromatic ring may have a nitro group or a substituent other than thenitro group bonded to the aromatic ring; R² represents a hydrogen atomor a hydrocarbon group which may have a substituent; and R³ represents ahydrogen atom, a carboxy group or a hydrocarbon group of 1 to 15 carbonatoms which may have a substituent, provided that part of the carbonatoms constituting the hydrocarbon group for R³ may be replaced with ahetero atom.

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon, unless otherwise specified.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom, anda “halogenated alkylene group” is a group in which part or all of thehydrogen atoms of an alkylene group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “hydroxyalkyl group” is a group in which part or all of the hydrogenatoms within an alkyl group have been substituted with a hydroxyl group.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

The term “boiling point” refers to a boiling point under a pressure of 1atm, unless otherwise specified.

According to the present invention, there are provided a method offorming a resist pattern which enables formation of a resist patternwith a high resolution and an excellent shape, and a resist compositionfor use in such method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of one embodiment ofthe method of forming a resist pattern according to the presentinvention.

FIG. 2 is a schematic diagram showing an example of another embodimentof the method of forming a resist pattern according to the presentinvention.

MODE FOR CARRYING OUT THE INVENTION

<<Resist Composition>>

The resist composition of the present invention includes a basecomponent (A) that exhibits increased solubility in an alkali developingsolution and a photobase generator component (C) that generates baseupon exposure, the resist composition being used in a method of forminga resist pattern including: a step (1) in which the resist compositionis applied to a substrate to form a resist film; a step (2) in which theresist film is subjected to exposure; a step (3) in which baking isconducted after the step (2), such that, at an exposed portion of theresist film, the base generated from the photobase generator component(C) upon the exposure and an acid provided to the resist film in advanceare neutralized, and at an unexposed portion of the resist film, thesolubility of the base component (A) in an alkali developing solution isincreased by the action of the acid provided to the resist film inadvance; and a step (4) in which the resist film is subjected to analkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved.

The resist composition of the present invention includes a basecomponent (A) (hereafter, referred to as “component (A)”) which exhibitschanged solubility in an alkali developing solution under action ofacid, and a photobase generator component (C) (hereafter, referred to as“component (C)”) which generates base upon exposure, and is used in thestep (1).

The method of forming a resist pattern including the steps (1) to (4) isdescribed later.

In the present invention, the “negative-tone resist pattern” is a resistpattern in which the unexposed portions of the resist film are dissolvedand removed by an alkali developing solution, and the exposed portionsremain as a pattern. A resist composition for forming the negative-toneresist pattern is sometimes referred to as a “negative-tone resistcomposition”. That is, the resist composition of the present inventionis a negative-tone resist composition.

An “acid provided to the resist film in advance” includes an acidderived from an acid supply component added to the resist compositionfor forming the resist film, and an acid derived from an acid supplycomponent that has been allowed to come in contact with the resist filmprior to baking in step (3).

As the acid supply component (hereafter, sometimes referred to as“component (Z)”), an acidic compound component (hereafter, sometimesreferred to as “component (G)”) or an acid-generator component(hereafter, sometimes referred to as “component (B)”) can be given as anexample.

An acidic compound refers to a compound which exhibits acidity itself,i.e., a compound that acts as a proton donor.

Examples of the acid generator include a thermal acid generator thatgenerates acid by heating, and a photoacid generator that generates acidupon exposure.

As the component (Z), one type of compound may be used, or two or moretypes of compounds may be used in combination. For example, an acidiccompound and an acid generator may be used in combination, or a thermalacid generator and a photoacid generator may be used in combination.Specific examples of the component (Z) will be described later.

Base Component: Component (A)

The component (A) is a base component which exhibits increasedsolubility in a developing solution under action of acid.

The term “base component” refers to an organic compound capable offorming a film, and is preferably an organic compound having a molecularweight of 500 or more. When the organic compound has a molecular weightof 500 or more, the film-forming ability is improved, and a resistpattern of nano level can be easily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. In the present description and claims, the term“resin” refers to a polymer having a molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

The component (A) is preferably a base component which exhibitsincreased polarity by the action of acid (hereafter, referred to as“component (A0)”).

In the present invention, when the component (A0) is used, since thepolarity of the component (A0) changes at unexposed portions before andafter the baking in the step (3), an excellent development contrast canbe obtained by an alkali development.

The component (A0) may be a resin component that exhibits increasedpolarity under the action of acid, a low molecular weight compound thatexhibits increased polarity under the action of acid, or a mixturethereof.

As the component (A0), a resin component that exhibits increasedpolarity under the action of acid is preferable, and a polymericcompound (A1) (hereafter, referred to as “component (A1)”) including astructural unit (a1) containing an acid decomposable group whichexhibits increased polarity by the action of acid is particularlydesirable.

The component (A1) preferably includes, in addition to the structuralunit (a1), a structural unit (a0) containing an —SO₂— containing cyclicgroup.

The component (A1) preferably includes, in addition to the structuralunit (a1) or the structural units (a0) and (a1), a structural unit (a2)derived from an acrylate ester which may have the hydrogen atom bondedto the carbon atom on the α-position substituted with a substituent andcontains a lactone-containing cyclic group.

In addition to the structural unit (a1) or in addition to the structuralunit (a1) and at least one of the structural unit (a0) and thestructural unit (a2), it is preferable that the component (A1) furtherinclude a structural unit (a3) derived from an acrylate ester containinga polar group-containing aliphatic hydrocarbon group and may have thehydrogen atom bonded to the carbon atom on the α-position substitutedwith a substituent.

In the present descriptions and the claims, the expression “structuralunit derived from an acrylate ester” refers to a structural unit that isformed by the cleavage of the ethylenic double bond of an acrylateester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent thatsubstitutes the hydrogen atom bonded to the carbon atom on theα-position is atom other than hydrogen or a group, and examples thereofinclude an alkyl group of 1 to 5 carbon atoms, a halogenated alkyl groupof 1 to 5 carbon atoms and a hydroxyalkyl group. A carbon atom on theα-position of an acrylate ester refers to the carbon atom bonded to thecarbonyl group, unless specified otherwise.

Hereafter, acrylic acid or an acrylate ester having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent is sometimes referred to as “α-substituted acrylic acid” or“α-substituted acrylate ester”.

Further, acrylic acid and α-substituted acrylic acid are collectivelyreferred to as “(α-substituted) acrylic acid”, and acrylate esters andα-substituted acrylate esters are collectively referred to as“(α-substituted) acrylate ester”.

In the α-substituted acrylate ester, the alkyl group as the substituenton the α-position is preferably a linear or branched alkyl group, andspecific examples thereof include a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsas the substituent on the α-position include groups in which part or allof the hydrogen atoms of the aforementioned “alkyl group of 1 to 5carbon atoms as the substituent on the α-position” are substituted withhalogen atoms. Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

It is preferable that a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms is bonded tothe α-position of the α-substituted acrylate ester, a hydrogen atom, analkyl group of 1 to 5 carbon atoms or a fluorinated alkyl group of 1 to5 carbon atoms is more preferable, and in terms of industrialavailability, a hydrogen atom or a methyl group is the most desirable.

[Structural Unit (a1)]

The structural unit (a1) is a structural unit containing an aciddecomposable group that exhibits increased polarity by the action ofacid.

The term “acid decomposable group” refers to a group in which at least apart of the bond within the structure thereof is cleaved by the actionof an acid.

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, anamino group and a sulfo group (—SO₃H). Among these, a polar groupcontaining —OH in the structure thereof (hereafter, referred to as“OH-containing polar group”) is preferable, a carboxy group or a hydroxygroup is more preferable, and a carboxy group is particularly desirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) can be given.

An “acid dissociable group” is a group in which at least the bondbetween the acid dissociable group and the adjacent carbon atom iscleaved by the action of acid. It is necessary that the acid dissociablegroup that constitutes the acid decomposable group is a group whichexhibits a lower polarity than the polar group generated by thedissociation of the acid dissociable group. Thus, when the aciddissociable group is dissociated by the action of acid, a polar groupexhibiting a higher polarity than that of the acid dissociable group isgenerated, thereby increasing the polarity. As a result, the polarity ofthe entire component (A1) is increased. By the increase in the polarity,the solubility in an alkali developing solution changes and, thesolubility in an alkali developing solution is relatively increased.

The acid dissociable group is not particularly limited, and any of thegroups that have been conventionally proposed as acid dissociable groupsfor the base resins of chemically amplified resists can be used.Generally, groups that form either a cyclic or chain-like tertiary alkylester with the carboxyl group of the (meth)acrylic acid, and acetal-typeacid dissociable groups such as alkoxyalkyl groups are widely known.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(═O)—O—). Inthis tertiary alkyl ester, the action of acid causes cleavage of thebond between the oxygen atom and the tertiary carbon atom, therebyforming a carboxy group.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable groups”.

Examples of tertiary alkyl ester-type acid dissociable groups includealiphatic branched, acid dissociable groups and aliphatic cyclicgroup-containing acid dissociable groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable group” is notlimited to be constituted of only carbon atoms and hydrogen atoms (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

As an example of the aliphatic branched, acid dissociable group, forexample, a group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) can begiven. (in the formula, each of R⁷¹ to R⁷³ independently represents alinear alkyl group of 1 to 5 carbon atoms). The group represented by theformula —C(R⁷¹)(R⁷²)(R⁷³) preferably has 4 to 8 carbon atoms, andspecific examples include a tert-butyl group, a 2-methyl-2-butyl group,a 2-methyl-2-pentyl group and a 3-methyl-3-pentyl group.

Among these, a tert-butyl group is particularly desirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

In the “aliphatic cyclic group-containing acid dissociable group”, the“aliphatic cyclic group” may or may not have a substituent. Examples ofthe substituent include an alkyl group of 1 to 5 carbon atoms, an alkoxygroup of 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkyl groupof 1 to 5 carbon atoms, and an oxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated alkyl group, may be used. Specific examples of aliphaticcyclic hydrocarbon groups include groups in which one or more hydrogenatoms have been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane. In these aliphaticcyclic hydrocarbon groups, part of the carbon atoms constituting thering may be replaced with an ethereal oxygen atom (—O—).

Examples of aliphatic cyclic group-containing acid dissociable groupsinclude

(i) a monovalent aliphatic cyclic group in which a substituent (a groupor an atom other than hydrogen) is bonded to the carbon atom on the ringskeleton to which an atom adjacent to the acid dissociable group (e.g.,“—O—” within “—C(═O)—O— group”) is bonded to form a tertiary carbonatom; and

(ii) a group which has a branched alkylene group containing a tertiarycarbon atom, and a monovalent aliphatic cyclic group to which thetertiary carbon atom is bonded.

In the group (i), as the substituent bonded to the carbon atom to whichan atom adjacent to the acid dissociable group on the ring skeleton ofthe aliphatic cyclic group, an alkyl group can be mentioned. Examples ofthe alkyl group include the same groups as those represented by R¹⁴ informulas (1-1) to (1-9) described later.

Specific examples of the group (i) include groups represented by generalformulas (1-1) to (1-9) shown below.

Specific examples of the group (ii) include groups represented bygeneral formulas (2-1) to (2-6) shown below.

In the formulas above, R¹⁴ represents an alkyl group; and g representsan integer of 0 to 8.

In the formulas above, each of R¹⁵ and R¹⁶ independently represents analkyl group.

In formulas (1-1) to (1-9), the alkyl group for R¹⁴ may be linear,branched or cyclic, and is preferably linear or branched.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples of such branched alkyl groupsinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group and a neopentyl group, and an isopropyl group isparticularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and stillmore preferably 1 or 2.

In formulas (2-1) to (2-6), as the alkyl group for R¹¹ and R¹⁶, the samealkyl groups as those for R¹⁴ can be used.

In formulas (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), one or more ofthe hydrogen atoms bonded to the carbon atoms constituting the ring maybe substituted with a substituent. Examples of the substituent includean alkyl group of 1 to 5 carbon atoms, a fluorine atom and a fluorinatedalkyl group.

An “acetal-type acid dissociable group” generally substitutes a hydrogenatom at the terminal of an OH-containing polar group such as a carboxygroup or hydroxyl group, so as to be bonded with an oxygen atom. Whenacid acts to break the bond between the acetal-type acid dissociablegroup and the oxygen atom to which the acetal-type, acid dissociablegroup is bonded, an OH-containing polar group such as a carboxy group ora hydroxy group is formed.

Examples of acetal-type acid dissociable groups include groupsrepresented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atomor an alkyl group of 1 to 5 carbon atoms; n represents an integer of 0to 3; and Y represents an alkyl group of 1 to 5 carbon atoms or analiphatic cyclic group.

In general formula (p1), n is preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 0.

As the lower alkyl group for R¹′ and R²′, the same lower alkyl groups asthose described above the alkyl groups as the substituent which may bebonded to the carbon atom on the α-position of the aforementionedα-substituted alkylester can be used, although a methyl group or ethylgroup is preferable, and a methyl group is particularly desirable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable group (p1) is a group represented by general formula (p1-1)shown below.

In the formula, R¹′, n and Y are the same as defined above.

As the alkyl group for Y, the same alkyl groups as those described abovethe for the substituent which may be bonded to the carbon atom on theα-position of the aforementioned α-substituted alkylester can bementioned.

As the aliphatic cyclic group for Y, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same aliphatic cyclic groups described above in connectionwith the “acid dissociable group containing an aliphatic cyclic group”can be used.

Further, as the acetal-type, acid dissociable group, groups representedby general formula (p2) shown below can also be used.

In the formula, R⁷ and R¹⁸ each independently represent a linear orbranched alkyl group or a hydrogen atom; and R¹⁹ represents a linear,branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, and the terminal of R¹⁷is bonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ormethyl group, and most preferably an ethyl group.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be used. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto, and the carbon atom having the oxygen atomand R¹⁷ bonded thereto. Such a cyclic group is preferably a 4- to7-membered ring, and more preferably a 4- to 6-membered ring. Specificexamples of the cyclic group include tetrahydropyranyl group andtetrahydrofuranyl group.

Examples of the structural unit (a1) include a structural unit derivedfrom an acrylate ester which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent andcontains an acid decomposable group which exhibits increased polarity bythe action of acid; a structural unit derived from hydroxystyrene or ahydroxystyrene derivative in which at least a part of the hydrogen atomof the hydroxy group is protected with a substituent containing an aciddecomposable group; and a structural unit derived from vinylbenzoic acidor a vinylbenzoic acid derivative in which at least a part of thehydrogen atom within —C(═O)—OH is protected with a substituentcontaining an acid decomposable group. Preferable examples of thesubstituent containing an acid decomposable group include the tertiaryalkyl ester-type acid dissociable group and the acetal-type aciddissociable group described above.

In the present description and claims, a “structural unit derived fromhydroxystyrene or a hydroxystyrene derivative” refers to a structuralunit that is formed by the cleavage of the ethylenic double bond ofhydroxystyrene or a hydroxystyrene derivative.

The term “hydroxystyrene derivative” includes compounds in which thehydrogen atom at the α-position of hydroxystyrene has been substitutedwith another substituent such as an alkyl group or a halogenated alkylgroup; and derivatives thereof. Here, the α-position (carbon atom on theα-position) refers to the carbon atom having the benzene ring bondedthereto, unless specified otherwise.

A “structural unit derived from vinylbenzoic acid or a vinylbenzoic acidderivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of vinylbenzoic acid or a vinylbenzoic acidderivative.

The term “vinylbenzoic acid derivative” includes compounds in which thehydrogen atom at the α-position of vinylbenzoic acid has beensubstituted with another substituent such as an alkyl group or ahalogenated alkyl group; and derivatives thereof. Here, the α-position(carbon atom on the α-position) refers to the carbon atom having thebenzene ring bonded thereto, unless specified otherwise.

As the structural unit (a1), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

Specific examples of the structural unit (a1) include a structural unitrepresented by general formula (a1-0-1) shown below and a structuralunit represented by general formula (a1-0-2) shown below.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X¹represents an acid dissociable group; Y² represents a divalent linkinggroup; and X² represents an acid dissociable group.

In general formula (a1-0-1), the alkyl group and the halogenated alkylgroup for R are respectively the same as defined for the alkyl group andthe halogenated alkyl group for the substituent which may be bonded tothe carbon atom on the α-position of the aforementioned substitutedacrylate ester. R is preferably a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a fluorinated alkyl group of 1 to 5 carbon atoms, andmost preferably a hydrogen atom or a methyl group.

X¹ is not particularly limited as long as it is an acid dissociablegroup. Examples thereof include the aforementioned tertiary alkylester-type acid dissociable groups and acetal-type acid dissociablegroups, and tertiary alkyl ester-type acid dissociable groups arepreferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

The divalent linking group for Y² is not particularly limited, andpreferable examples thereof include a divalent hydrocarbon group whichmay have a substituent and a divalent linking group containing a heteroatom.

A hydrocarbon “has a substituent” means that part or all of the hydrogenatoms within the hydrocarbon group is substituted with a substituent (agroup or an atom other than hydrogen).

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group.

An “aliphatic hydrocarbon group” refers to a hydrocarbon group that hasno aromaticity.

The divalent aliphatic hydrocarbon group as the divalent hydrocarbongroup for Y² may be either saturated or unsaturated. In general, thedivalent aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4,and most preferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O).

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which two hydrogenatoms have been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group, and a group inwhich the alicyclic group is interposed within the aforementioned linearor branched aliphatic hydrocarbon group, can be given. As the linear orbranched aliphatic hydrocarbon group, the same groups as those describedabove can be used.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic aliphatic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic group, a group in which two hydrogen atoms have been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The alicyclic hydrocarbon group may or may not have a substituent.Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring.

The aromatic hydrocarbon group as the divalent hydrocarbon group for Y²preferably has 3 to 30 carbon atoms, more preferably 5 to 30, still morepreferably 5 to 20, still more preferably 6 to 15, and most preferably 6to 10. Here, the number of carbon atoms within a substituent(s) is notincluded in the number of carbon atoms of the aromatic hydrocarbongroup.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring (arylene group); and a group in which onehydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group) and one hydrogen atom has been substitutedwith an alkylene group (such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

The aromatic hydrocarbon group may or may not have a substituent. Forexample, the hydrogen atom bonded to the aromatic hydrocarbon ringwithin the aromatic hydrocarbon group may be substituted with asubstituent. Examples of substituents include an alkyl group, an alkoxygroup, a halogen atom, a halogenated alkyl group, a hydroxyl group andan oxygen atom (═O).

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

With respect to a “divalent linking group containing a hetero atom” forY², a hetero atom is an atom other than carbon and hydrogen, andexamples thereof include an oxygen atom, a nitrogen atom, a sulfur atomand a halogen atom.

Examples of the divalent linking group containing a hetero atom include—O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH— (H may besubstituted with a substituent such as an alkyl group or an acyl group),—S—, —S(═O)₂—, —S(═O)₂—O—, —NH—C(═O)—, ═N—, and a group represented bygeneral formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²— or—Y²¹—O—C(═O)—Y²²— [wherein Y²¹ and Y²² each independently represents adivalent hydrocarbon group which may have a substituent, O represents anoxygen atom, and m′ represents an integer of 0 to 3.]

When Y² represents —NH—, H may be substituted with a substituent such asan alkyl group, an aryl group (an aromatic group) or the like. Thesubstituent (an alkyl group, an aryl group or the like) preferably has 1to 10 carbon atoms, more preferably 1 to 8, and most preferably 1 to 5.

In formula —Y²¹—O—Y²²—, —[Y²¹C(═O)—O]_(m′)—Y²²— or —Y²¹—O—C(═O)—Y²², Y²¹and Y²² each independently represents a divalent hydrocarbon group whichmay have a substituent. As the divalent hydrocarbon group, the samegroups as those described above for the “divalent hydrocarbon groupwhich may have a substituent” for Y² can be mentioned.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m′)—Y²²—, m′represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m′)—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

As the divalent linking group containing a hetero atom, a linear groupcontaining an oxygen atom as the hetero atom e.g., a group containing anether bond or an ester bond is preferable, and a group represented bythe aforementioned formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²— or—Y²¹—O—C(═O)—Y²²— is more preferable.

Among the aforementioned examples, as the divalent linking group for Y²,an alkylene group, a divalent alicyclic hydrocarbon group or a divalentlinking group containing a hetero atom is particularly desirable. Amongthese, an alkylene group or a divalent linking group containing a heteroatom is more preferable.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

In the formulas, R¹, R¹′, R²′, n, Y and Y² are the same as definedabove; and X¹ represents a tertiary alkyl ester-type acid dissociablegroup.

In the formulas, the tertiary alkyl ester-type acid dissociable groupfor X′ include the same tertiary alkyl ester-type acid dissociablegroups as those described above.

As R¹′, R²′, n and Y are respectively the same as defined for R¹′, R²′,n and Y in general formula (p1) described above in connection with the“acetal-type acid dissociable group”.

As examples of Y², the same groups as those described above for Y² ingeneral formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

In the present invention, as the structural unit (a1), it is preferableto include at least one structural unit selected from the groupconsisting of a structural unit represented by general formula (a1-0-11)shown below, a structural unit represented by general formula (a1-0-12)shown below, a structural unit represented by general formula (a1-0-13)shown below, a structural unit represented by general formula (a1-0-14)shown below, a structural unit represented by general formula (a1-0-15)shown below and a structural unit represented by general formula(a1-0-2) shown below.

Among these examples, as the structural unit (a1), it is preferable toinclude at least one structural unit selected from the group consistingof a structural unit represented by general formula (a1-0-11) shownbelow, a structural unit represented by general formula (a1-0-12) shownbelow, a structural unit represented by general formula (a1-0-13) shownbelow, a structural unit represented by general formula (a1-0-14) shownbelow and a structural unit represented by general formula (a1-0-15)shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²¹represents an alkyl group; R²² represents a group which forms analiphatic monocyclic group with the carbon atom to which R²² is bonded;R²³ represents a branched alkyl group; R²⁴ represents a group whichforms an aliphatic polycyclic group with the carbon atom to which R²⁴ isbonded; R²⁵ represents a linear alkyl group of 1 to 5 carbon atoms; R¹⁵and R¹⁶ each independently represents an alkyl group; Y² represents adivalent linking group; and X² an acid dissociable group.

In the formulas, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R²¹, the same alkylgroups as those described above for R¹⁴ in formulas (1-1) to (1-9) canbe used, preferably a methyl group, an ethyl group or an isopropylgroup.

As the aliphatic monocyclic group formed by R²² and the carbon atoms towhich R²² is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociablegroup and which are monocyclic can be used. Specific examples includegroups in which one or more hydrogen atoms have been removed from amonocycloalkane. The monocycloalkane is preferably a 3- to 11-memberedring, more preferably a 3- to 8-membered ring, still more preferably a4- to 6-membered ring, and most preferably a 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atomsconstituting the ring replaced with an ether bond (—O—).

Further, the monocycloalkane may have a substituent such as an alkylgroup of 1 to 5 carbon atoms, a fluorine atom or a fluorinated alkylgroup of 1 to 5 carbon atoms.

As an examples of R²² constituting such an aliphatic cyclic group, analkylene group which may have an ether bond (—O—) interposed between thecarbon atoms can be given.

Specific examples of structural units represented by general formula(a1-0-11) include structural units represented by the aforementionedformulas (a1-0-16) to (a1-1-23), (a1-1-27) and (a1-1-31). Among these, astructural unit represented by general formula (a1-1-02) shown belowwhich includes the structural units represented by the aforementionedformulas (a1-0-16), (a1-1-17), (a1-1-20) to (a1-1-23), (a1-1-27),(a1-1-31), (a1-1-32) and (a1-1-33) is preferable. Further, a structuralunit represented by general formula (a1-1-02′) shown below is alsopreferable.

In the formulas, h represents an integer of 1 to 4, and preferably 1 or2.

In the formulae, R and R²¹ are the same as defined above; and hrepresents an integer of 1 to 4.

In general formula (a1-0-12), as the branched alkyl group for R²³, thesame alkyl groups as those described above for R¹⁴ which are branchedcan be used, and an isopropyl group is particularly desirable.

As the aliphatic polycyclic group formed by R²⁴ and the carbon atoms towhich R²⁴ is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociablegroup and which are polycyclic can be used.

Specific examples of structural units represented by general formula(a1-0-12) include structural units represented by the aforementionedformulas (a1-0-26) and (a1-1-28) to (a1-1-30).

As the structural unit (a1-0-12), a structural unit in which thealiphatic polycyclic group formed by R²⁴ and the carbon atom to whichR²⁴ is bonded is a 2-adamantyl group is preferable, and a structuralunit represented by the aforementioned formula (a1-0-26) is particularlydesirable.

In general formula (a1-0-13), R and R²⁴ are the same as defined above.

As the linear alkyl group for R²⁵, the same linear alkyl groups as thosedescribed above for R¹⁴ in the aforementioned formulas (1-1) to (1-9)can be mentioned, and a methyl group or an ethyl group is particularlydesirable.

Specific examples of structural units represented by general formula(a1-0-13) include structural units represented by the aforementionedformulas (a1-1-1), (a1-1-2) and (a1-1-7) to (a1-1-15) which weredescribed above as specific examples of the structural unit representedby general formula (a1-1).

As the structural unit (a1-0-13), a structural unit in which thealiphatic polycyclic group formed by R²⁴ and the carbon atom to whichR²⁴ is bonded is a 2-adamantyl group is preferable, and a structuralunit represented by the aforementioned formula (a1-0-1) or (a1-1-2) isparticularly desirable.

In general formula (a1-0-14), R and R²² are the same as defined above.R¹⁵ and R¹⁶ are the same as R¹⁵ and R¹⁶ in the aforementioned generalformulae (2-1) to (2-6), respectively.

Specific examples of structural units represented by general formula(a1-0-14) include structural units represented by the aforementionedformulae (a1-0-35) and (a1-1-36) which were described above as specificexamples of the structural unit represented by general formula (a1-1).

In general formula (a1-0-15), R and R²⁴ are the same as defined above.R¹⁵ and R¹⁶ are the same as R¹⁵ and R¹⁶ in the aforementioned generalformulae (2-1) to (2-6), respectively.

Specific examples of structural units represented by general formula(a1-0-15) include structural units represented by the aforementionedformulae (a1-0-4) to (a1-1-6) and (a1-1-34) which were described aboveas specific examples of the structural unit represented by generalformula (a1-1).

Examples of structural units represented by general formula (a1-0-2)include structural units represented by the aforementioned formulas(a1-3) and (a1-4).

As a structural unit represented by general formula (a1-0-2), those inwhich Y² is a group represented by the aforementioned formula—Y²¹—O—Y²²— or —Y²¹—C(═O)—O—Y²²— is particularly desirable.

Preferable examples of such structural units include a structural unitrepresented by general formula (a1-0-01) shown below, a structural unitrepresented by general formula (a1-1-02) shown below, and a structuralunit represented by general formula (a1-0-03) shown below.

In the formulas, R is the same as defined above; R¹³ represents ahydrogen atom or a methyl group; R¹⁴ represents an alkyl group; erepresents an integer of 1 to 10; and n′ represents an integer of 0 to3.

In the formula, R is as defined above; each of Y²′ and Y²″ independentlyrepresents a divalent linking group; X′ represents an acid dissociablegroup; and w represents an integer of 0 to 3.

In general formulas (a1-0-01) and (a1-3-02), R¹³ is preferably ahydrogen atom.

R¹⁴ is the same as defined for R¹⁴ in the aforementioned formulas (1-1)to (1-9).

e is preferably an integer of 1 to 8, more preferably an integer of 1 to5, and most preferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula(a1-0-01) include structural units represented by the aforementionedformulas (a1-0-25) and (a1-3-26).

Specific examples of structural units represented by general formula(a1-1-02) include structural units represented by the aforementionedformulas (a1-0-27) and (a1-3-28).

In general formula (a1-0-03), as the divalent linking group for Y²′ andY²″, the same groups as those described above for Y² in general formula(a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable group for X′, the same groups as those describedabove can be used. X′ is preferably a tertiary alkyl ester-type aciddissociable group, more preferably the aforementioned group (i) in whicha substituent is bonded to the carbon atom to which an atom adjacent tothe acid dissociable group is bonded to on the ring skeleton to form atertiary carbon atom. Among these, a group represented by theaforementioned general formula (1-1) is particularly desirable.

w represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), astructural unit represented by general formula (a1-3-03-1) or(a1-3-03-2) shown below is preferable, and a structural unit representedby general formula (a1-3-03-1) is particularly desirable.

In the formulas, R and R¹⁴ are the same as defined above; a′ representsan integer of 1 to 10; b′ represents an integer of 1 to 10; and trepresents an integer of 0 to 3.

In general formulas (a1-0-03-1) and (a1-3-03-2), a′ is the same asdefined above, preferably an integer of 1 to 8, more preferably 1 to 5,and most preferably 1 or 2.

b′ is the same as defined above, preferably an integer of 1 to 8, morepreferably 1 to 5, and most preferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

Specific examples of structural units represented by general formula(a1-0-03-1) or (a1-3-03-2) include structural units represented by theaforementioned formulas (a1-0-29) to (a1-3-32).

As the structural unit (a1) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

In the component (A1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1) is preferably 15 to 70 mol %, more preferably 15 to 60 mol %, andstill more preferably 20 to 55 mol %.

When the amount of the structural unit (a1) is at least as large as thelower limit of the above-mentioned range, a pattern can be easily formedusing a resist composition prepared from the component (A1), and variouslithography properties such as sensitivity, resolution, LWR and the likeare improved. On the other hand, when the amount of the structural unit(a1) is no more than the upper limit of the above-mentioned range, agood balance can be reliably achieved with the other structural units.

[Structural Unit (a0)]

The structural unit (a0) is a structural unit containing an —SO₂—containing cyclic group.

By virtue of the structural unit (a0) containing a —SO₂— containingcyclic group, a resist composition containing the component (A1)including the structural unit (a0) is capable of improving the adhesionof a resist film to a substrate. Further, the —SO₂— containing cyclicgroup contributes to improvement in various lithography properties suchas sensitivity, resolution, exposure latitude (EL margin), line widthroughness (LWR), line edge roughness (LER) and mask reproducibility.

Here, an “—SO₂— containing cyclic group” refers to a cyclic group havinga ring containing —SO₂— within the ring structure thereof, i.e., acyclic group in which the sulfur atom (S) within —SO₂— forms part of thering skeleton of the cyclic group.

In the —SO₂— containing cyclic group, the ring containing —SO₂— withinthe ring skeleton thereof is counted as the first ring. A cyclic groupin which the only ring structure is the ring that contains —SO₂— in thering skeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings.

The —SO₂— containing cyclic group may be either a monocyclic group or apolycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable.

The —SO₂— containing cyclic group preferably has 3 to 30 carbon atoms,more preferably 4 to 20, still more preferably 4 to 15, and mostpreferably 4 to 12. Herein, the number of carbon atoms refers to thenumber of carbon atoms constituting the ring skeleton, excluding thenumber of carbon atoms within a substituent.

The —SO₂— containing cyclic group may be either a —SO₂— containingaliphatic cyclic group or a —SO₂— containing aromatic cyclic group. A—SO₂— containing aliphatic cyclic group is preferable.

Examples of the —SO₂— containing aliphatic cyclic group includealiphatic cyclic groups in which part of the carbon atoms constitutingthe ring skeleton has been substituted with a —SO₂— group or a —O—SO₂—group and has at least one hydrogen atom removed from the aliphatichydrocarbon ring. Specific examples include an aliphatic hydrocarbonring in which a —CH₂— group constituting the ring skeleton thereof hasbeen substituted with a —SO₂— group and has at least one hydrogen atomremoved therefrom; and an aliphatic hydrocarbon ring in which a—CH₂—CH₂— group constituting the ring skeleton has been substituted witha —O—SO₂— group and has at least one hydrogen atom removed therefrom.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic group, a group in which two hydrogenatoms have been removed from a monocycloalkane of 3 to 6 carbon atoms ispreferable. Examples of the monocycloalkane include cyclopentane andcyclohexane. As the polycyclic group, a group in which two hydrogenatoms have been removed from a polycycloalkane of 7 to 12 carbon atomsis preferable. Examples of the polycycloalkane include adamantane,norbornane, isobornane, tricyclodecane and tetracyclododecane.

The —SO₂— containing cyclic group may have a substituent. Examples ofthe substituent include an alkyl group, an alkoxy group, a halogen atom,a halogenated alkyl group, a hydroxy group, an oxygen atom (═O), —COOR″,—OC(═O)R″, a hydroxyalkyl group and a cyano group (wherein R″ representsa hydrogen atom or an alkyl group).

The alkyl group for the substituent is preferably an alkyl group of 1 to6 carbon atoms. Further, the alkyl group is preferably a linear alkylgroup or a branched alkyl group. Specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group and a hexyl group. Among these, amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

As the alkoxy group for the substituent, an alkoxy group of 1 to 6carbon atoms is preferable. Further, the alkoxy group is preferably alinear or branched alkoxy group. Specific examples of the alkoxy groupinclude the aforementioned alkyl groups for the substituent having anoxygen atom (—O—) bonded thereto.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

As examples of the halogenated alkyl group for the substituent, groupsin which part or all of the hydrogen atoms of the aforementioned alkylgroups for the substituent have been substituted with the aforementionedhalogen atoms can be given. As the halogenated alkyl group, afluorinated alkyl group is preferable, and a perfluoroalkyl group isparticularly desirable.

In the —COOR″ group and the —OC(═O)R″ group, R″ preferably represents ahydrogen atom or a linear, branched or cyclic alkyl group of 1 to 15carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

More specific examples of the —SO₂— containing cyclic group includegroups represented by general formulas (3-1) to (3-4) shown below.

In the formulas, A′ represents an oxygen atom, a sulfur atom or analkylene group of 1 to 5 carbon atoms which may contain an oxygen atomor a sulfur atom; z represents an integer of 0 to 2; and R⁶ representsan alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.

In general formulas (3-1) to (3-4) above, A′ represents an oxygen atom(—O—), a sulfur atom (—S—) or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom.

As the alkylene group of 1 to 5 carbon atoms represented by A′, a linearor branched alkylene group is preferable, and examples thereof include amethylene group, an ethylene group, an n-propylene group and anisopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atominclude the aforementioned alkylene groups in which —O— or —S— is bondedto the terminal of the alkylene group or present between the carbonatoms of the alkylene group. Specific examples of such alkylene groupsinclude —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, —CH₂—S—CH₂—.

As A′, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

z represents an integer of 0 to 2, and is most preferably 0.

When z is 2, the plurality of R⁶ may be the same or different from eachother.

As the alkyl group, alkoxy group, halogenated alkyl group, —COOR″,—OC(═O)R″ and hydroxyalkyl group for R⁶, the same alkyl groups, alkoxygroups, halogenated alkyl groups, —COOR″, —OC(═O)R″ and hydroxyalkylgroups as those described above as the substituent for the —SO₂—containing cyclic group can be mentioned.

Specific examples of the cyclic groups represented by general formulas(3-1) to (3-4) are shown below. In the formulas shown below, “Ac”represents an acetyl group.

As the —SO₂— containing cyclic group, a group represented by theaforementioned general formula (3-1) is preferable, at least one memberselected from the group consisting of groups represented by theaforementioned chemical formulas (a1-0-1), (3-1-18), (3-3-1) and (3-4-1)is more preferable, and a group represented by chemical formula (3-1-1)is most preferable.

More specifically, examples of the structural unit (a0) includestructural units represented by general formula (a0-0) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R³⁹represents —O— or —NH—; R³⁰ represents a —SO₂— containing cyclic group;and R²⁹′ represents a single bond or a divalent linking group.

In general formula (a0-0), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms.

As the alkyl group of 1 to 5 carbon atoms for R, a linear or branchedalkyl group of 1 to 5 carbon atoms is preferable, and specific examplesthereof include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group.

The halogenated alkyl group for R is a group in which part or all of thehydrogen atoms of the aforementioned alkyl group of 1 to 5 carbon atomshas been substituted with halogen atoms. Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In the formula (a0-0), R³⁹ represents —O— or —NH—.

In formula (a0-0), R³⁰ is the same as defined for the aforementioned—SO₂— containing group.

In the formula (a0-0), R²⁹′ may be either a single bond or a divalentlinking group. In terms of the effects of the present invention andlithography properties, a divalent linking group is preferable.

As the divalent linking group for R²⁹, for example, the same divalentlinking groups as those described for Y² in general formula (a1-0-2)explained above in relation to the structural unit (a1) can bementioned.

As the divalent linking group for R²⁹′, an alkylene group, a divalentalicyclic hydrocarbon group or a divalent linking group containing ahetero atom is preferable. Among these, an alkylene group or a divalentlinking group containing an ester bond (—C(═O)—O—) is preferable.

As the alkylene group, a linear or branched alkylene group ispreferable. Specific examples include the same linear alkylene groupsand branched alkylene groups as those described above for the aliphatichydrocarbon group represented by Y².

As the divalent linking group containing an ester bond, a grouprepresented by general formula: —R²⁰—C(═O)—O— (in the formula, R²⁰represents a divalent linking group) is particularly desirable. Namely,the structural unit (a0) is preferably a structural unit represented bygeneral formula (a0-0-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R³⁹represents —O— or —NH—; R²⁰ represents a divalent linking group; and R³⁰represents an —SO₂— containing cyclic group.

R²⁰ is not particularly limited. For example, the same divalent linkinggroups as those described for R²⁹′ in general formula (a0-0) can bementioned.

As the divalent linking group for R²⁰, an alkylene group, a divalentalicyclic hydrocarbon group or a divalent linking group containing ahetero atom is preferable.

As the linear or branched alkylene group, the divalent alicyclichydrocarbon group and the divalent linking group containing a heteroatom, the same linear or branched alkylene group, divalent alicyclichydrocarbon group and divalent linking group containing a hetero atom asthose described above as preferable examples of R²⁹′ can be mentioned.

Among these, a linear or branched alkylene group, or a divalent linkinggroup containing an oxygen atom as a hetero atom is more preferable.

As the linear alkylene group, a methylene group or an ethylene group ispreferable, and a methylene group is particularly desirable.

As the branched alkylene group, an alkylmethylene group or analkylethylene group is preferable, and —CH(CH₃)—, —C(CH₃)₂— or—C(CH₃)₂CH₂— is particularly desirable.

As the divalent linking group containing a hetero atom, a divalentlinking group containing an ether bond or an ester bond is preferable,and a group represented by the aforementioned formula —Y²¹—O—Y²²—,—[Y²¹—C(═O)—O]_(m′)—Y²²— or —Y²¹—O—C(═O)—Y²²— is more preferable. Y²¹,Y²² and m′ are the same as defined above.

Among these, a group represented by the formula —Y²¹—O—C(═O)—Y²²—, and agroup represented by the formula —(CH₂)_(c)—O—C(═O)—(CH₂)_(d)— isparticularly desirable. c represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2. d represents an integerof 1 to 5, preferably an integer of 1 to 3, and more preferably 1 or 2.

In particular, as the structural unit (a0), a structural unitrepresented by general formula (a0-0-11) or (a0-0-12) shown below ispreferable, and a structural unit represented by general formula(a0-0-12) is more preferable.

In the formulae, R, A′, R⁶, z, R³⁹ and R²⁰ are the same as definedabove.

In general formula (a0-0-11), A′ is preferably a methylene group, anethylene group, an oxygen atom (—O—) or a sulfur atom (—S—).

In formula (a0-0-12), as R²⁰, a linear or branched alkylene group or adivalent linking group containing an oxygen atom is preferable. As thelinear or branched alkylene group and the divalent linking groupcontaining an oxygen atom represented by R²⁰, the same linear orbranched alkylene groups and the divalent linking groups containing anoxygen atom as those described above can be mentioned.

As the structural unit represented by general formula (a0-0-12), astructural unit represented by general formula (a0-0-12a) or (a0-0-12b)shown below is particularly desirable.

In the formulae, R, R³⁹ and A′ are the same as defined above; c and dare the same as defined above; and f represents an integer of 1 to 5(preferably an integer of 1 to 3).

As the structural unit (a0) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

In terms of achieving an excellent shape for a resist pattern formedusing a positive resist composition containing the component (A1) andexcellent lithography properties such as EL margin, LWR and maskreproducibility, the amount of the structural unit (a0) within thecomponent (A1), based on the combined total of all structural unitsconstituting the component (A1) is preferably 1 to 60 mol %, morepreferably 5 to 55 mol %, still more preferably 10 to 50 mol %, and mostpreferably 15 to 45 mol %.

[Structural Unit (a2)]

The structural unit (a2) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains alactone-containing cyclic group.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the component (A1) is used for forming a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate, andincreasing the compatibility with the developing solution containingwater (especially in an alkali developing process).

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include agroup in which one hydrogen atom has been removed from a 4- to6-membered lactone ring, such as a group in which one hydrogen atom hasbeen removed from β-propionolatone, a group in which one hydrogen atomhas been removed from γ-butyrolactone, and a group in which one hydrogenatom has been removed from δ-valerolactone. Further, specific examplesof lactone-containing polycyclic groups include groups in which onehydrogen atom has been removed from a lactone ring-containingbicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; eachR′ independently represents a hydrogen atom, an alkyl group, an alkoxygroup, a halogen atom, a halogenated alkyl group, a hydroxy group, anoxygen atom (═O), —COOR″, OC(═O)R″, a hydroxyalkyl group or a cyanogroup, wherein R″ represents a hydrogen atom or an alkyl group; R²⁹represents a single bond or a divalent linking group; s″ represents aninteger of 0 to 2; A″ represents an oxygen atom, a sulfur atom or analkylene group of 1 to 5 carbon atoms which may contain an oxygen atomor a sulfur atom; and m represents 0 or 1.

In general formulas (a2-1) to (a2-5), R is the same as defined for R inthe structural unit (a1).

As the alkyl group, alkoxy group, halogen atom, halogenated alkyl group,—COOR″, —OC(═O)R″ and hydroxyalkyl group for R′, the same alkyl groups,alkoxy groups, halogen atoms, halogenated alkyl groups, —COOR″,—OC(═O)R″ (R″ is the same as defined above) and hydroxyalkyl groups asthose described above as the substituent for the —SO₂— containing cyclicgroup can be mentioned.

As A″, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

R²⁹ represents a single bond or a divalent linking group. Examples ofdivalent linking groups include the same divalent linking groups asthose described above for Y² in general formula (a1-0-2). Among these,an alkylene group, an ester bond (—C(═O)—O—) or a combination thereof ispreferable. The alkylene group as a divalent linking group for R²⁹ ispreferably a linear or branched alkylene group. Specific examplesinclude the same linear alkylene groups and branched alkylene groups asthose described above for the aliphatic hydrocarbon group represented byY².

s″ is preferably 1 or 2.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a2) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

As the structural unit (a2), at least one structural unit selected fromthe group consisting of formulas (a2-1) to (a2-5) is preferable, and atleast one structural unit selected from the group consisting of formulas(a2-1) to (a2-3) is more preferable. Of these, it is preferable to useat least one structural unit selected from the group consisting ofstructural units represented by formulas (a2-0-1), (a2-1-2), (a2-2-1),(a2-2-7), (a2-3-1) and (a2-3-5).

In the component (A1), the amount of the structural unit (a2) based onthe combined total of all structural units constituting the component(A1) is preferably 5 to 60 mol %, more preferably 10 to 60 mol %, andstill more preferably 10 to 50 mol %.

When the amount of the structural unit (a2) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a2) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a2) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units.

[Structural Unit (a3)]

The structural unit (a3) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains a polargroup-containing aliphatic hydrocarbon group (provided that theaforementioned structural units (a1), (a0) and (a2) are excluded fromthe structural unit (a3)).

When the component (A1) includes the structural unit (a3), thehydrophilicity of the component (A1) is enhanced, thereby contributingto improvement in resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups can be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. 1 is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

The amount of the structural unit (a3) within the component (A1) basedon the combined total of all structural units constituting the component(A1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a3) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a3) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units.

[Other Structural Unit]

The component (A1) may also have a structural unit other than theabove-mentioned structural units (a1), (a0), (a2) and (a3), as long asthe effects of the present invention are not impaired.

As such a structural unit, any other structural unit which cannot beclassified as the aforementioned structural units can be used withoutany particular limitation, and any of the multitude of conventionalstructural units used within resist resins for ArF excimer lasers or KrFexcimer lasers (and particularly for ArF excimer lasers) can be used.

Examples of the other structural unit include a structural unit (a4)derived from an acrylate ester which may have the hydrogen atom bondedto the carbon atom on the α-position substituted with a substituent andcontains an acid non-dissociable aliphatic polycyclic group, astructural unit (a5) derived from hydroxystyrene and a structural unit(a6) derived from styrene.

A “structural unit derived from a hydroxystyrene” refers to a structuralunit that is formed by the cleavage of the ethylenic double bond of ahydroxystyrene.

The term “hydroxystyrene” is a generic term that includes hydroxystyrenehaving a hydrogen atom bonded to the carbon atom on the α-position (thecarbon atom to which the phenyl group is bonded), hydroxystyrene havinga substituent (an atom other than a hydrogen atom or a group) bonded tothe carbon atom on the α-position, and derivatives thereof.Specifically, at least the benzene ring and the hydroxy group bonded tothe benzene ring are maintained, and examples thereof include those inwhich the hydrogen atom bonded to the α-position of hydroxystyrene hasbeen substituted with an alkyl group of 1 to 5 carbon atoms, ahalogenated alkyl group of 1 to 5 carbon atoms, a hydroxyalkyl group orthe like, and those in which the benzene ring having a hydroxy groupbonded thereto further has an alkyl group of 1 to 5 carbon atoms, orthose in which the benzene ring having a hydroxy group bonded theretofurther has one or two hydroxy groups (the total number of hydroxygroups being two or three).

A “structural unit derived from styrene” refers to a structural unitthat is formed by the cleavage of the ethylenic double bond of styrene.

The term “styrene” includes styrene, compounds in which the hydrogenatom at the α-position has been substituted with a substituent (an atomother than hydrogen or a group), and derivatives thereof (provided thatthe aforementioned hydroxystyrene is excluded). Further, those in whicha hydrogen atom of the phenyl group has been substituted with asubstituent such as an alkyl group of 1 to 5 carbon atoms are alsoincluded.

In the aforementioned hydroxystyrene or styrene, the alkyl group as thesubstituent on the α-position is preferably a linear or branched alkylgroup, and specific examples thereof include a methyl group, an ethylgroup, a propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, a tert-butyl group, a pentyl group, an isopentyl group and aneopentyl group.

Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsas the substituent on the α-position include groups in which part or allof the hydrogen atoms of the aforementioned “alkyl group of 1 to 5carbon atoms as the substituent on the α-position” are substituted withhalogen atoms. Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

Specific examples of the hydroxyalkyl group of 1 to 5 carbon atoms asthe substituent on the α-position include groups in which part or all ofthe hydrogen atoms of the aforementioned “alkyl group of 1 to 5 carbonatoms as the substituent on the α-position” are substituted with ahydroxy group. The number of hydroxy groups within the hydroxyalkylgroup is preferably 1 to 5, and most preferably 1.

(Structural Unit (a4))

The structural unit (a4) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains an acidnon-dissociable aliphatic polycyclic group.

In the structural unit (a4), examples of this polycyclic group includethe same polycyclic groups as those described above in relation to theaforementioned structural unit (a1), and any of the multitude ofconventional polycyclic groups used within the resin component of resistcompositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecyl group, adamantylgroup, tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable. These polycyclic groups may be substituted witha linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-5) shown below.

In the formulae, R is the same as defined above.

When the structural unit (a4) is included in the component (A1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

(Structural Unit (a5))

As the structural unit (a5), a structural unit represented by generalformula (a5-1) shown below is preferable because the solubility in anorganic solvent becomes excellent, the solubility in an alkalideveloping solution is increased, and the etching resistance becomesexcellent.

In the formula, R⁶⁰ represents a hydrogen atom or an alkyl group of 1 to5 carbon atoms; R⁶¹ represents an alkyl group of 1 to 5 carbon atoms; prepresents an integer of 1 to 3; and q represents an integer of 0 to 2.

In the formula (a5-1), specific examples of the alkyl group of 1 to 5carbon atoms for R⁶⁰ include linear or branched alkyl groups such as amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group. As R⁶⁰, a hydrogen atom or amethyl group is preferable.

p represents an integer of 1 to 3, and is preferably 1.

The bonding position of the hydroxy group may be any of the o-position,m-position and p-position of the phenyl group. When p is 1, thep-position is preferable in terms of availability and low cost. When pis 2 or 3, a desired combination of the bonding positions can be used.

q represents an integer of 0 to 2. q is preferably 0 or 1, and mostpreferably 0 from industrial viewpoint.

As the alkyl group for R⁶¹, the same alkyl groups as those for R⁶⁰ canbe mentioned.

When q is 1, the bonding position of R⁶¹ may be any of the o-position,the m-position and the p-position.

When q is 2, a desired combination of the bonding positions can be used.Here, the plurality of the R⁶¹ group may be the same or different fromeach other.

When the structural unit (a5) is included in the component (A1), theamount of the structural unit (a5) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 50 to 90 mol %, more preferably from 55 to 85 mol%, and still more preferably 60 to 80 mol %.

(Structural Unit (a6))

As the structural unit (a6), a structural unit represented by generalformula (a6-1) shown below is preferable because the solubility in analkali developing solution can be adjusted, and heat resistance and dryetching resistance are improved.

In the formula, R⁶⁰ represents a hydrogen atom or an alkyl group of 1 to5 carbon atoms; R⁶² represents an alkyl group of 1 to 5 carbon atoms;and x represents an integer of 0 to 3.

In general formula (a6-1), R⁶⁰ is the same as defined above for R⁶⁰ inthe aforementioned general formula (a5-1).

In the formula (a6-1), as the alkyl group for R⁶², the same alkyl groupsas those for R⁶¹ in the aforementioned formula (a5-1) can be mentioned.

x represents an integer of 0 to 3, preferably 0 or 1, and mostpreferably 0 in terms of industry.

When x represents 1, the substitution position of R⁶² may be any ofo-position, m-position or p-position of the phenyl group. When x is 2 or3, a desired combination of the bonding positions can be used. Here, theplurality of the R⁶² group may be the same or different from each other.

When the structural unit (a6) is included in the component (A1), theamount of the structural unit (a6) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 10 to 50 mol %, more preferably from 15 to 45 mol%, and still more preferably 20 to 40 mol %.

In the resist composition of the present invention, the component (A)preferably contains a polymeric compound (A1) having a structural unit(a1).

Specific examples of the component (A1) include a polymeric compoundconsisting of a repeating structure of a structural unit (a1) and astructural unit (a2); a polymeric compound consisting of a repeatingstructure of a structural unit (a1) and a structural unit (a0); apolymeric compound consisting of a repeating structure of a structuralunit (a1), a structural unit (a2) and a structural unit (a3); apolymeric compound consisting of a repeating structure of a structuralunit (a1), a structural unit (a0) and a structural unit (a3); and apolymeric compound consisting of a repeating structure of a structuralunit (a1), a structural unit (a0), a structural unit (a2) and astructural unit (a3).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (A1)is not particularly limited, but is preferably 1,000 to 50,000, morepreferably 1,500 to 30,000, and most preferably 2,000 to 20,000. Whenthe weight average molecular weight is no more than the upper limit ofthe above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is not particularly limited, but ispreferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably1.0 to 2.5. Here, Mn is the number average molecular weight.

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

As the monomers for deriving the corresponding structural units,commercially available monomers may be used, or the monomers may besynthesized by a conventional method.

In the component (A), as the component (A1), one type may be used alone,or two or more types may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, various lithography propertiesare improved, such as improvement in MEF and circularity, and reductionof roughness.

The component (A) may contain “a base component which exhibits increasedpolarity under action of acid” other than the component (A1) (hereafter,referred to as “component (A2)”), as long as the effects of the presentinvention are not impaired.

Examples of the component (A2) include low molecular weight compoundsthat have a molecular weight of at least 500 and less than 2,500,contains a hydrophilic group, and also contains an acid dissociablegroup described above in connection with the component (A1). Specificexamples include compounds containing a plurality of phenol skeletons inwhich part or all of the hydrogen atoms within hydroxyl groups have beensubstituted with the aforementioned acid dissociable groups.

Examples of the low-molecular weight compound include low molecularweight phenolic compounds in which a portion of the hydroxyl grouphydrogen atoms have been substituted with an aforementioned aciddissociable group, and these types of compounds are known, for example,as sensitizers or heat resistance improvers for use in non-chemicallyamplified g-line or i-line resists.

Examples of these low molecular weight phenol compounds includebis(4-hydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane,2-(4-hydroxyphenyl)-2-(4′-hydroxyphenyl)propane,2-(2,3,4-trihydroxyphenyl)-2-(2′,3′,4′-trihydroxyphenyl)propane,tris(4-hydroxyphenyl)methane,bis(4-hydroxy-3,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-3,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-3-methylphenyl)-3,4-dihydroxyphenylmethane,bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-4-hydroxyphenylmethane,bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-3,4-dihydroxyphenylmethane,1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene,and dimers, trimers, tetramers, pentamers and hexamers of formalincondensation products of phenols such as phenol, m-cresol, p-cresol andxylenol. Needless to say, the low molecular weight phenol compound isnot limited to these examples. In particular, a phenol compound having 2to 6 triphenylmethane skeletons is preferable in terms of resolution andline width roughness (LWR). Also, there are no particular limitations onthe acid dissociable group, and suitable examples include the groupsdescribed above.

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

Photobase Generator Component; Component (C)

In the resist composition of the present invention, the component (C)includes a compound (C1) represented by general formula (C1) shown below(hereafter, this compound is sometimes referred to as “component (C1)”).

In the method of forming a resist pattern according to the presentinvention, by virtue of the component (C) being decomposed in step (2)by the exposure energy to generate a base, an excellent dissolutioncontrast can be obtained, and a negative-tone resist pattern having anexcellent dimension uniformity can be formed.

In formula (C1), R¹ represents a group which forms an aromatic ringtogether with the two carbon atoms bonded to the R¹ group, provided thatthe aromatic ring may have a nitro group or a substituent other than thenitro group bonded to the aromatic ring; R² represents a hydrogen atomor a hydrocarbon group which may have a substituent; and R³ represents ahydrogen atom, a carboxy group or a hydrocarbon group of 1 to 15 carbonatoms which may have a substituent, provided that part of the carbonatoms constituting the hydrocarbon group for R³ may be replaced with ahetero atom.

[Component (C1)]

When the component (C1) is irradiated by radiation (subjected toexposure), at least the bond between the nitrogen atom within the6-membered ring in the formula (C1) and the carbon atom of the carbonylgroup (C═O) adjacent to the nitrogen atom is cleaved, thereby generatingan amine and carbon dioxide.

In formula (C1), R¹ represents a group which forms an aromatic ringtogether with the two carbon atoms bonded to the R¹ group, provided thatthe aromatic ring may have a nitro group or a substituent other than thenitro group bonded to the aromatic ring.

The aromatic ring formed by R¹ and 2 carbon atoms to which R¹ is bondedis not particularly limited as long as it is a cyclic conjugatedcompound having (4n+2)π electrons (wherein n represents 0 or a naturalnumber), and may be either monocyclic or polycyclic. The aromatic ringpreferably has 5 to 30 carbon atoms, more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12.

Examples of the aromatic ring include aromatic hydrocarbon rings, suchas benzene, naphthalene, anthracene, phenanthrene, indene and fluorene;and aromatic hetero rings in which part of the carbon atoms constitutingthe aforementioned aromatic hydrocarbon rings has been substituted witha hetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include pyridine andthiophene.

Examples of the substituent group for the aromatic ring in addition tothe nitro group already bonded include a nitro group, an oxo group (═O),an alkyl group, an alkoxy group, a halogen atom, a halogenated alkylgroup, a hydroxyalkyl group, a hydroxy group, —COOR″, —OC(═O)R″, a cyanogroup, —NR″₂, —R⁹′—N(R¹⁰′)—C(═O)—O—R⁵′, and a nitrogen-containingheterocyclic group.

Specific examples of aromatic hetero rings having an oxo group (═O)include anthraquinone, thioxanthone and xanthone.

The alkyl group as the substituent for the aromatic ring is preferablyan alkyl group of 1 to 6 carbon atoms. Further, the alkyl group ispreferably a linear alkyl group or a branched alkyl group.

Specific examples include a methyl group, an ethyl group, a propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group, a neopentyl groupand a hexyl group. Among these, a methyl group or ethyl group ispreferable, and a methyl group is particularly desirable.

The alkoxy group as the substituent for the aromatic ring is preferablyan alkoxy group of 1 to 6 carbon atoms. Further, the alkoxy group ispreferably a linear or branched alkoxy group. Specific examples of thealkoxy group include the aforementioned alkyl groups for the substituenthaving an oxygen atom (—O—) bonded thereto.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

As examples of the halogenated lower alkyl group for the substituent,groups in which part or all of the hydrogen atoms of the aforementionedalkyl groups for the substituent have been substituted with theaforementioned halogen atoms can be given. As the halogenated alkylgroup, a fluorinated alkyl group is preferable, and a perfluoroalkylgroup is particularly desirable.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

In the —COOR″ group, the —OC(═O)R″ group and the —NR″₂ group, R″represents a hydrogen atom or a linear, branched or cyclic alkyl groupof 1 to 15 carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The two R″ groups within the —NR″₂ group may be the same or differentfrom each other.

In formula —R⁹′—N(R¹⁰′)—C(═O)—O—R⁵′, R⁹′ represents a divalenthydrocarbon group which may contain a hetero atom, R¹⁰′ represents ahydrogen atom or a monovalent hydrocarbon group which may contain ahetero atom, and R⁵′ represents a monovalent organic group which has analiphatic ring or an aromatic ring.

The hydrocarbon group for R¹⁰′ may be an aromatic hydrocarbon group oran aliphatic hydrocarbon group.

The aromatic hydrocarbon group for R¹⁰′ is a hydrocarbon group having atleast one aromatic ring. As the aromatic ring, the same aromatic ringsas those described above for “the aromatic ring formed by theaforementioned R¹ and 2 carbon atoms bonded to R¹” can be mentioned.Specific examples of the aromatic hydrocarbon group for R¹⁰′ include agroup in which one hydrogen atom has been removed from theaforementioned aromatic hydrocarbon ring or aromatic hetero ring (arylgroup or heteroaryl group); a group in which one hydrogen atom has beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (an arylalkyl group such asa benzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethylgroup, or a heteroarylalkyl group). The alkylene group which substitutesthe hydrogen atom of the aforementioned aromatic hydrocarbon ring or thearomatic hetero ring preferably has 1 to 4 carbon atoms, more preferably1 or 2 carbon atoms, and most preferably 1 carbon atom.

The aliphatic hydrocarbon group for R¹⁰′ refers to a hydrocarbon groupthat has no aromaticity.

The aliphatic hydrocarbon group for R¹⁰′ may be either saturated (analkyl group) or unsaturated. In general, the aliphatic hydrocarbon groupis preferably saturated. Further, the aliphatic hydrocarbon group may belinear, branched or cyclic, or a combination thereof. Examples of thecombination include a group in which a cyclic aliphatic hydrocarbongroup is bonded to a terminal of a linear or branched aliphatichydrocarbon group, and a group in which a cyclic aliphatic hydrocarbongroup is interposed within a linear or branched aliphatic hydrocarbongroup.

The linear or branched alkyl group preferably has 1 to 20 carbon atoms,more preferably 1 to 15, and still more preferably 1 to 10.

Specific examples of linear alkyl groups include a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup, a heptyl group, an octyl group, a nonyl group, a decyl group, anundecyl group, a dodecyl group, a tridecyl group, an isotridecyl group,a tetradecyl group, a pentadecyl group, a hexadecyl group, anisohexadecyl group, a heptadecyl group, an octadecyl group, a nonadecylgroup, an icosyl group, a henicosyl group and a docosyl group.

Specific examples of branched alkyl groups include a 1-methylethyl group(an isopropyl group), a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a tert-butyl group, a1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group anda 4-methylpentyl group.

The cyclic alkyl group may be either a monocyclic group or a polycyclicgroup. The aliphatic cyclic group preferably has 3 to 30 carbon atoms,more preferably 5 to 30, still more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12. As the aliphatic cyclicgroup, a group in which one hydrogen atom has been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane can be used. Specific examples of thegroup in which one hydrogen atom has been removed from a monocycloalkaneinclude a cyclopentyl group and a cyclohexyl group. Examples of thegroup in which one hydrogen atom has been removed from a polycycloalkaneinclude an adamantyl group, a norbornyl group, an isobornyl group, atricyclodecyl group and a tetracyclododecyl group.

The aromatic hydrocarbon group and the aliphatic hydrocarbon group forR¹⁰′ may have a substituent. As the substituent, the same substituentsas those described above for “the aromatic ring formed by theaforementioned R¹ and 2 carbon atoms bonded to R¹” can be mentioned.

Examples of the hydrocarbon group for R⁹′ include groups in which onehydrogen atom has been removed from the hydrocarbon group (aromatichydrocarbon group or aliphatic hydrocarbon group) for R¹⁰′.

The aliphatic ring or the aromatic ring for R⁵′ may be either ahydrocarbon ring or a hetero ring, and preferable examples thereofinclude groups explained above for R¹⁰′ which have a ring structure, andother aromatic rings. Specific examples of the above hydrocarbon ringand hetero ring include benzene, biphenyl, indene, naphthalene,fluorene, anthracene, phenanthrene, xanthone, thioxanthone andanthraquinone.

Further, these hydrocarbon rings and hetero rings may have asubstituent. In terms of base generation efficiency, as the substituent,a nitro group is particularly desirable.

In formula —R⁹′—N(R¹⁰′)—C(═O)—O—R⁵′, R¹⁰′ may be bonded to R⁹′ to form aring.

The “nitrogen-containing heterocyclic group” as the aforementionedsubstituent for the aromatic ring is a group in which one or morehydrogen atoms have been removed from a nitrogen-containing heterocycliccompound containing a nitrogen atom in the ring skeleton thereof. Thenitrogen-containing heterocyclic compound may have a carbon atom or ahetero atom other than nitrogen (e.g., an oxygen atom, a sulfur atom orthe like) within the ring skeleton thereof.

The nitrogen-containing heterocyclic compound may be either aromatic oraliphatic. When the nitrogen-containing heterocyclic compound isaliphatic, it may be either saturated or unsaturated. Further, thenitrogen-containing heterocyclic compound may be either monocyclic orpolycyclic.

The nitrogen-containing heterocyclic compound preferably has 3 to 30carbon atoms, more preferably 5 to 30, and still more preferably 5 to20.

Specific examples of monocyclic nitrogen-containing heterocyclo compoundinclude pyrrole, pyridine, imidazole, pyrazole, 1,2,3-triazole,1,2,4-triazole, pyrimidine, pyrazine, 1,3,5-triazine, tetrazole,piperidine, piperazine, pyrrolidine and morpholine.

Specific examples of polycyclic nitrogen-containing heterocyclo compoundinclude quinoline, isoquinoline, indole, pyrrolo[2,3-b]pyridine,indazole, benzimidazole, benzotriazole, carbazole, acridine,1,5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene,hexamethylenetetramine and 1,4-diazabicyclo[2.2.2]octane.

The nitrogen-containing heterocyclic compound may have a substituent. Asthe substituent, the same substituents as those described above for “thearomatic ring formed by the aforementioned R¹ and 2 carbon atoms bondedto R¹” can be mentioned.

In formula (C1), R² represents a hydrogen atom or a hydrocarbon groupwhich may have a substituent.

The hydrocarbon group for R² may be an aromatic hydrocarbon group or analiphatic hydrocarbon group. The aromatic hydrocarbon group and thealiphatic hydrocarbon group for R² is the same as defined for thearomatic hydrocarbon group and the aliphatic hydrocarbon group for R¹⁰′.

When R² is an aromatic hydrocarbon group, in terms of base generationefficiency, R² is preferably a group represented by general formula(C1-r2) shown below.

In the formula, the valence bond is denoted “*”

In the formula, R¹⁰¹ represents a group which forms an aromatic ringtogether with the two carbon atoms bonded to the R¹⁰¹ group, providedthat the aromatic ring may have a nitro group or a substituent otherthan the nitro group bonded to the aromatic ring.

In formula (C1-r2), the aromatic ring formed by R¹⁰¹ and 2 carbon atomsto which R¹⁰¹ is bonded, and the substituent for the aromatic ring arethe same as defined for the “aromatic ring formed by R¹ and 2 carbonatoms to which R¹ is bonded” in formula (C1), and the substituent forthe aromatic ring.

Examples of the substituent for the hydrocarbon group represented by R²include the same substituents as those described above for thehydrocarbon group represented by R¹⁰′. By introducing a substituent tothe hydrocarbon group for R², the base generation efficiency (i.e., thereaction efficiency at photofunctional portions) and the photoadsorptionefficiency can be controlled.

In formula (C1), R³ represents a hydrogen atom, a carboxy group or ahydrocarbon group of 1 to 15 carbon atoms which may have a substituent

As the hydrocarbon group for R³, the same hydrocarbon groups as thosefor R² which have 1 to 15 carbon atoms can be mentioned. As thesubstituent for the hydrocarbon group, the same substituents as thosedescribed above for the hydrocarbon group represented by R² can bementioned.

However, part of the carbon atoms constituting the hydrocarbon group forR³ may be replaced with a hetero atom. The hetero atom is an atom otherthan carbon and hydrogen, and examples thereof include an oxygen atom, anitrogen atom, a sulfur atom and a halogen atom. Examples of the halogenatom include a fluorine atom, a chlorine atom, a bromine atom and aniodine atom.

As R³, a group represented by general formula (C1-r3) shown below ispreferable.

In the formula, R⁴ represents a hydrocarbon group of 1 to 15 carbonatoms which may have a substituent, provided that part of the carbonatoms constituting the hydrocarbon group for R⁴ may be replaced with ahetero atom.

In formula (C1-r3), as the hydrocarbon group for R⁴, the samehydrocarbon groups as those for R² which have 1 to 15 carbon atoms canbe mentioned. As the substituent for the hydrocarbon group, the samesubstituents as those described above for the hydrocarbon grouprepresented by R² can be mentioned.

However, part of the carbon atoms constituting the hydrocarbon group forR⁴ may be replaced with a hetero atom. The hetero atom is an atom otherthan carbon and hydrogen, and examples thereof include an oxygen atom, anitrogen atom, a sulfur atom and a halogen atom. Examples of the halogenatom include a fluorine atom, a chlorine atom, a bromine atom and aniodine atom.

The hydrocarbon group for R⁴ preferably contains a cyclic group becausethe effect of suppressing diffusion length of the base generated uponexposure is improved.

Specific examples of the component (C1) are shown below.

As the component (C1), one type of compound may be used, or two or moretypes of compounds may be used in combination.

As the component (C1), at least one member selected from the groupconsisting of compounds represented by general formulae (C1-1) to (C1-8)above is preferable, and

at least one member selected from the group consisting of compoundsrepresented by general formulae (C1-1) to (C1-4), (C1-6) and (C1-7) ismore preferable.

In the resist composition, the amount of the component (C1) within thecomponent (C) is preferably 50% by weight or more, still more preferably75% by weight or more, and may be even 100% by weight. When the amountof the component (C1) is at least as large as the lower limit of theabove-mentioned range, the dimension uniformity of the formed resistpattern is improved.

In the resist composition, the amount of the component (C1), relative to100 parts by weight of the component (A) is preferably from 0.05 to 50parts by weight, more preferably from 1 to 30 parts by weight, and mostpreferably from 5 to 20 parts by weight.

When the amount of the component (C1) is at least as large as the lowerlimit of the above-mentioned range, the film retentiveness of the resistfilm at exposed portions becomes excellent, and the dimension uniformityof the formed resist pattern is further improved. Further, theresolution and the pattern shape of the formed resist pattern becomesexcellent. On the other hand, when the amount of the component (C1) isno more than the upper limit of the above-mentioned range, thetransparency of the resist film can be maintained.

[Component (C2)]

The resist composition of the present invention may contain a photobasegenerator which does not fall under the definition of the component (C1)(heerafter, such photobase generator is sometimes referred to as“component (C2”), as long as the effects of the present invention arenot impaired.

The component (C2) may be any compound capable of being decomposed byirradiation of radiation to generate a base, and examples thereofinclude a compound containing a carbamate group (a urethane bond), acompound containing an acyloxyimino group, an ionic compound (ananion-cation complex), and a compound containing a carbamoyloxyiminogroup. Among these, a compound containing a carbamate group (a urethanebond), a compound containing an acyloxyimino group, and an ioniccompound (an anion-cation complex) are preferable.

Further, compounds having a ring structure within a molecule thereof arepreferable, and examples thereof include compounds having a ringskeleton such as benzene, naphthalene, anthracene, xanthone,thioxanthone, anthraquinone or fluorene.

Component (C21)

As the component (C2), in terms of photodegradability, a compoundrepresented by general formula (C2-1) shown below (hereafter, referredto as “component (C21)”) is preferable. When the component (C21) isirradiated by radiation, at least the bond between the nitrogen atom inthe formula (C2-1) and the carbon atom of the carbonyl group adjacent tothe nitrogen atom is cleaved, thereby generating an amine or ammonia andcarbon dioxide. After the decomposition, it is preferable that theproduct containing —N(R⁰¹)(R⁰²) has a high boiling point. Further, interms of suppressing diffusion during PEB, it is preferable that theproduct containing —N(R⁰¹)(R⁰²) has a large molecular weight or a highlybulky skeleton.

In the formula, R⁰¹ and R⁰² each independently represents a hydrogenatom or a monovalent hydrocarbon group which may contain a hetero atom,provided that R⁰¹ and R⁰² may be mutually bonded to form a cyclic groupwith the adjacent nitrogen atom; and R⁰³ represents a monovalentphotoactive group.

In formula (C2-1), the hetero atom which may be contained in thehydrocarbon group for R⁰¹ and R⁰² is an atom other than hydrogen andcarbon, and examples thereof include an oxygen atom, a nitrogen atom, asulfur atom and a halogen atom. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom.

The hydrocarbon group may be either an aromatic hydrocarbon group or analiphatic hydrocarbon group, and is preferably an aliphatic hydrocarbongroup.

The aromatic hydrocarbon group and the aliphatic hydrocarbon group forR⁰¹ and R⁰² is the same as defined for the aromatic hydrocarbon groupand the aliphatic hydrocarbon group for R¹⁰′.

The aromatic hydrocarbon group for R⁰¹ and R⁰² may have a substituent.For example, part of the carbon atoms constituting the aromatic ringwithin the aromatic hydrocarbon group may be substituted with a heteroatom, or a hydrogen atom bonded to the aromatic ring within the aromatichydrocarbon group may be substituted with a substituent.

Further, when the aromatic hydrocarbon group has an aliphatichydrocarbon group bonded to the aromatic ring, part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with asubstituent group containing a hetero atom, or part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group. As examples of the “aliphatichydrocarbon group” and the “divalent linking group containing a heteroatom”, the same aliphatic hydrocarbon groups and divalent linking groupscontaining a hetero atom as those described later for R⁰¹ and R⁰² can bementioned.

Examples of the aromatic hydrocarbon group in which part of the carbonatoms constituting the aromatic ring has been substituted with a heteroatom include a heteroaryl group in which part of the carbon atomsconstituting the aromatic ring has been substituted with a hetero atomsuch as an oxygen atom, a sulfur atom or a nitrogen atom, and aheteroarylalkyl group in which part of the carbon atoms constituting thearomatic hydrocarbon ring within the aforementioned arylalkyl group hasbeen substituted with the aforementioned heteroatom.

Examples of the substituent group which substitutes the hydrogen atombonded to the aromatic ring of the aforementioned aromatic hydrocarbongroup include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyalkyl group, a hydroxy group, an oxogroup (═O), —COOR″, —OC(═O)R″, a cyano group, a nitro group, —NR″₂,—R⁹′—N(R¹⁰′)—C(═O)—O—R⁵′, and a nitrogen-containing heterocyclic group,and the explanation for these groups are the same as those describedabove as the substituent for the “aromatic ring formed by R¹ and the twocarbon atoms bonded to the R′ group”.

The aliphatic hydrocarbon group for R⁰¹ and R⁰² may have a substituent.For example, part of the carbon atoms constituting the aliphatichydrocarbon group may be replaced by a divalent linking group containinga hetero atom, and part or all of the hydrogen atoms constituting thealiphatic hydrocarbon group may be substituted with a substituent.

With respect to the divalent linking group containing a hetero atom,examples of hetero atoms include the same hetero atoms as thosedescribed above which replaces part of the carbon atoms constituting thearomatic ring contained in the aforementioned aromatic hydrocarbongroup. Examples of the divalent linking group containing a hetero atominclude divalent non-hydrocarbon groups containing a hetero atom, suchas —O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —S—,—S(═O)₂—, —S(═O)₂—O—, —NH—, —NR⁰⁴—(R⁰⁴ represents a substituent such asan alkyl group or an acyl group), —NH—C(═O)— and ═N—. Further, acombination of any one of these “non-hydrocarbon groups containing ahetero atom” with a divalent aliphatic hydrocarbon group can also beused. Examples of the divalent aliphatic hydrocarbon group includegroups in which one hydrogen atom has been removed from theaforementioned aliphatic hydrocarbon group, and a linear or branchedaliphatic hydrocarbon group is preferable.

As the substituent for the aliphatic hydrocarbon group in the latterexample (the case where part or all of the hydrogen atoms constitutingthe aliphatic hydrocarbon group may be substituted with a substituent),the same groups as those described above for the substituent group whichsubstitutes a hydrogen atom bonded to the aromatic ring contained in theaforementioned aromatic hydrocarbon group can be mentioned.

In the formula (C2-1), R⁰¹ and R⁰² may be mutually bonded to form acyclic group with the adjacent nitrogen atom.

The cyclic group may be either an aromatic cyclic group or an aliphaticcyclic group. When the cyclic group is an aliphatic cyclic group, it maybe either saturated or unsaturated. In general, the aliphatic cyclicgroup is preferably saturated.

The cyclic group may have a nitrogen atom other than the nitrogen atombonded to R⁰¹ and R⁰² within the ring skeleton thereof. Further, thecyclic group may have a carbon atom or a hetero atom other than nitrogen(e.g., an oxygen atom, a sulfur atom or the like) within the ringskeleton thereof.

The cyclic group may be either a monocyclic group or a polycyclic group.

When the cyclic group is monocyclic, the number of atoms constitutingthe skeleton of the cyclic group is preferably from 4 to 7, and morepreferably 5 or 6. That is, the cyclic group is preferably a 4- to7-membered ring, and more preferably a 5- or 6-membered ring. Specificexamples of monocyclic groups include groups in which the hydrogen atomof —NH— has been removed from a heteromonocyclic group containing —NH—in the ring structure thereof, such as piperidine, pyrrolidine,morpholine, pyrrole, imidazole, pyrazole, 1,2,3-triazole,1,2,4-triazole, tetrazole or piperazine.

When the cyclic group is polycyclic, the cyclic group is preferablybicyclic, tricyclic or tetracyclic. Further, the number of atomsconstituting the skeleton of the cyclic group is preferably from 7 to12, and more preferably from 7 to 10. Specific examples of polycyclicnitrogen-containing heterocyclic groups include groups in which thehydrogen atom of —NH— has been removed from a heteropolycyclic groupcontaining —NH— in the ring structure thereof, such as indole,isoindole, carbazole, benzimidazole, indazole or benzotriazole.

The cyclic group may have a substituent. Examples of the substituentinclude the same groups as those described above for the substituentgroup which substitutes a hydrogen atom bonded to the aromatic ringcontained in the aforementioned aromatic hydrocarbon group.

As a cyclic group formed by R⁰¹ and R⁰² mutually bonded with theadjacent nitrogen atom, a group represented by general formula (II)shown below is particularly desirable.

In the formula, R⁰⁵ and R⁰⁶ each independently represents a hydrogenatom or an alkyl group; R⁰⁷ represents a linear alkylene group of 1 to 3carbon atoms which may have a carbon atom substituted with an oxygenatom or a nitrogen atom and may have a hydrogen atom substituted with asubstituent.

In formula (II), as the alkyl group for R⁰⁵ and R⁰⁶, the same alkylgroups as those described above as the aliphatic hydrocarbon group forR⁰¹ and R⁰² can be mentioned, a linear or branched alkyl group ispreferable, and a methyl group is particularly desirable.

Examples of the alkylene group for R⁰⁷ which may have a carbon atomsubstituted with an oxygen atom or a nitrogen atom include —CH₂—,—CH₂—O—, —CH₂—NH—, —CH₂—CH₂—, —CH₂—O—CH₂—, —CH₂—NH—CH₂—, —CH₂—CH₂—CH₂—,—CH₂—CH₂—O—CH₂—, and —CH₂—CH₂—NH—CH₂—.

As the substituent which substitutes a hydrogen atom in the alkylenegroup, the same groups as those described above for the substituentgroup which substitutes a hydrogen atom bonded to the aromatic ringcontained in the aforementioned aromatic hydrocarbon group can bementioned. The hydrogen atom to be substituted with a substituent may bea hydrogen atom bonded to a carbon atom, or a hydrogen atom bonded to anitrogen atom in the case where the carbon atom is replaced by anitrogen atom.

In formula (C2-1), R⁰³ represents a monovalent photoactive group.

The term “photoactive group” refers to a group which absorbs theexposure energy of the exposure conducted in step (2).

As the photoactive group, a ring-containing group is preferable, and maybe either a hydrocarbon ring or a hetero ring. Preferable examplesthereof include groups having a ring structure described above for R⁰¹and R⁰², and groups having an aromatic ring. Specific examples ofpreferable ring skeletons for the ring-containing group include benzene,biphenyl, indene, naphthalene, fluorene, anthracene, phenanthrene,xanthone, thioxanthone and anthraquinone.

Further, these ring skeletons may have a substituent. In terms ofefficiency in the generation of a base, as the substituent, a nitrogroup is particularly desirable.

As the component (C21), a compound represented by general formula(C2-11) or (C2-12) shown below is particularly desirable.

In the formulae, R^(4a) and R^(4b) each independently represents a ringskeleton selected from benzene, biphenyl, indene, naphthalene, fluorene,anthracene, phenanthrene, xanthone, thioxanthone and anthraquinone whichmay have a substituent; R^(1a) and R^(2a) each independently representsa hydrogen atom, an alkyl group of 1 to 15 carbon atoms, a cycloalkylgroup or an aryl group; R^(11a) represents an alkyl group of 1 to 5carbon atoms; m″ represents 0 or 1; n″ represents 0 to 3; and each p″independently represents 0 to 3.

In formulae (C2-11) and (C2-12), in terms of efficiency in generation ofa base, it is preferable that R^(4a) and R^(4b) has a nitro group as asubstituent, and it is particularly desirable that the ortho position issubstituted.

It is preferable that each of R^(1a) and R^(2a) independently representsa hydrogen atom, a cycloalkyl group or an aryl group, and in terms ofsuppressing the diffusion length of the generated base, a cycloalkylgroup of 5 to 10 carbon atoms is more preferable. The aryl group forR^(1a) and R^(2a) is preferably a phenyl group.

m″ is preferably 1. n″ is preferably 0 to 2. p″ is preferably 0 or 1.

Specific examples of the component (C21) are shown below.

Component (C22)

Further, as a preferable example of the component (C2), a compoundrepresented by general formula (C2-2) shown below (hereafter, referredto as “component (C22)”) can also be mentioned.

After absorbing the exposure energy by the exposure conducted in step(2), the component (C22) has the (—CH═CH—C(═O)—) portion isomerized to acis isomer, and is further cyclized by heating, thereby generating abase (NHR⁰¹R⁰²).

The component (C22) is preferable in that, not only a base can begenerated, but also the effect of rendering the resist compositionhardly soluble in an alkali developing solution in step (4) can beobtained.

In the formula, R⁰¹ and R⁰² are respectively the same as defined for R⁰¹and R⁰² in the aforementioned formula (C2-1); and R³′ represents anaromatic cyclic group having a hydroxy group on the ortho position.

In the aforementioned formula (C-22), it is preferable that R⁰¹ and R⁰²are mutually bonded together with the adjacent nitrogen atom to form acyclic group represented by the aforementioned formula (II). Further,R⁰¹ and R⁰² are preferably the same as defined for R^(1a) and R^(2a) inthe aforementioned formula (C2-12).

As the aromatic cyclic group for R³′, the same groups having an aromaticring as those described above for R⁰³ in the aforementioned formula(C2-1) can be mentioned. As the ring skeleton, benzene, biphenyl,indene, naphthalene, fluorene, anthracene and phenanthrene arepreferable, and a benzene ring is more preferable.

The aromatic cyclic group for R³′ may have a substituent other than thehydroxy group on the ortho position. Examples of the substituent includea halogen atom, a hydroxy group, a mercapto group, a sulfide group, asilyl group, a silanol group, a nitro group, a nitroso group, a sulfinogroup, a sulfo group, a sulfonate group, a phosphino group, a phosphinylgroup, a phosphono group, a phosphonate group, an amino group, anammonio group, and a monovalent organic group such as an alkyl group.

Specific examples of the component (C22) are shown below.

Component (C23)

Further, as a preferable example of the component (C2), a compoundrepresented by general formula (C2-3) shown below (hereafter, referredto as “component (C23)”) can also be mentioned.

After absorbing the exposure energy by the exposure conducted in step(2), the component (C23) undergoes decarboxylation, and then reacts withwater to generate amine (base).

In the formula, R^(a) and R^(d) each independently represents a hydrogenatom or a hydrocarbon group of 1 to 30 carbon atoms which may have asubstituent (provided that, when both R^(a) and R^(d) represent ahydrocarbon group of 1 to 30 carbon atoms which may have a substituent,R^(a) and R^(d) are mutually bonded to form a ring); and R^(b)represents an aryl group which may have a substituent or an aliphaticcyclic group which may have a substituent.

In the aforementioned formula (C2-3), R^(a) represents a hydrogen atomor a hydrocarbon group of 1 to 30 carbon atoms which may have asubstituent.

The hydrocarbon group of 1 to 30 carbon atoms for R^(a) which may have asubstituent may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

The aromatic hydrocarbon group for R^(a) is a hydrocarbon group havingat least one aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having 4n+2π electrons (wherein n represents 0 or anatural number), and may be either monocyclic or polycyclic. Thearomatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to20, still more preferably 6 to 15, and most preferably 6 to 12. Here,the number of carbon atoms within a substituent(s) is not included inthe number of carbon atoms of the aromatic hydrocarbon group.

Examples of the aromatic ring include aromatic hydrocarbon rings, suchas benzene, naphthalene, anthracene and phenanthrene; and aromatichetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include a pyridine ringand a thiophene ring.

Specific examples of the aromatic hydrocarbon group for R^(a) include agroup in which one hydrogen atom has been removed from theaforementioned aromatic hydrocarbon ring or aromatic hetero ring (arylgroup or heteroaryl group); a group in which one hydrogen atom has beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (an arylalkyl group such asa benzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethylgroup, or a heteroarylalkyl group). The alkylene group which substitutesthe hydrogen atom of the aforementioned aromatic hydrocarbon ring or thearomatic hetero ring preferably has 1 to 4 carbon atoms, more preferably1 or 2 carbon atoms, and most preferably 1 carbon atom.

The aromatic hydrocarbon group for R^(a) may have a substituent. Forexample, part of the carbon atoms constituting the aromatic ring withinthe aromatic hydrocarbon group may be substituted with a hetero atom, ora hydrogen atom bonded to the aromatic ring within the aromatichydrocarbon group may be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxo group (═O) or the like can beused.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxygroup, n-butoxy group or tert-butoxy group, and most preferably amethoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for theaforementioned aromatic hydrocarbon group include groups in which partor all of the hydrogen atoms within an alkyl group of 1 to 5 carbonatoms (e.g., a methyl group, an ethyl group, a propyl group, an n-butylgroup or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The aliphatic hydrocarbon group for R^(a) in the aforementioned formula(C2-3) may be either a saturated aliphatic hydrocarbon group, or anunsaturated aliphatic hydrocarbon group. Further, the aliphatichydrocarbon group may be linear, branched or cyclic.

In the aliphatic hydrocarbon group for R^(a) in the aforementionedformula (C2-3), part of the carbon atoms constituting the aliphatichydrocarbon group may be substituted with a substituent group containinga hetero atom, or part or all of the hydrogen atoms constituting thealiphatic hydrocarbon group may be substituted with a substituent groupcontaining a hetero atom.

As the “hetero atom” for R^(a) in the aforementioned formula (C2-3),there is no particular limitation as long as it is an atom other thancarbon and hydrogen, and examples thereof include a halogen atom, anoxygen atom, a sulfur atom and a nitrogen atom. Examples of the halogenatom include a fluorine atom, a chlorine atom, an iodine atom and abromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatichydrocarbon group is cyclic, the aliphatic hydrocarbon group may containany of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphaticcyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10.Specific examples include a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decyl group, an undecyl group, a dodecylgroup, a tridecyl group, an isotridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecylgroup, an octadecyl group, a nonadecyl group, an icosyl group, ahenicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to10. Specific examples include a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5, still more preferably 2 to 4, and mostpreferably 3. Examples of linear monovalent unsaturated hydrocarbongroups include a vinyl group, a propenyl group (an allyl group) and abutynyl group. Examples of branched monovalent unsaturated hydrocarbongroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The cyclic aliphatic hydrocarbon group (aliphatic cyclic group) forR^(a) in the aforementioned formula (C2-3) is an aliphatic cyclic groupof 3 to 30 carbon atoms which may have a substituent.

In the aliphatic cyclic group for R^(a) in the aforementioned formula(C2-3), part of the carbon atoms constituting the aliphatic cyclic groupmay be substituted with a substituent group containing a hetero atom, orpart or all of the hydrogen atoms constituting the aliphatic cyclicgroup may be substituted with a substituent group containing a heteroatom.

As the “hetero atom” for R^(a) in the aforementioned formula (C2-3),there is no particular limitation as long as it is an atom other thancarbon and hydrogen, and examples thereof include a halogen atom, anoxygen atom, a sulfur atom and a nitrogen atom. Examples of the halogenatom include a fluorine atom, a chlorine atom, an iodine atom and abromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. These substituents may becontained in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group has 3 to 30 carbon atoms,preferably 5 to 30, more preferably 5 to 20, still more preferably 6 to15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulas (L1) to (L6) and (S1) to(S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms,—O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m represents 0or 1.

In the formulas, the alkylene group for Q″ and R⁹⁴ to R⁹⁵ is preferablya linear or branched alkylene group, and has 1 to 5 carbon atoms,preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—, and —CH(CH₂CH3)CH₂—; a trimethylene group (n-propylene group) [—CH₂CH₂CH₂—];alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups suchas —CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group[—CH₂CH₂CH₂CH₂CH₂—].

In these aliphatic cyclic groups, part of the hydrogen atoms bonded tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as thesubstituent groups for substituting part or all of the hydrogen atomscan be used.

As the aliphatic cyclic group for R^(a) which may have a substituent inthe formula (C2-3), an aliphatic polycyclic group which may have asubstituent is preferable. As the aliphatic polycyclic group, theaforementioned group in which one or more hydrogen atoms have beenremoved from a polycycloalkane, and groups represented by formulas (L2)to (L6), (S3) and (S4) are preferable.

When R^(a) in the aforementioned formula (C2-3) represents a hydrocarbongroup of 1 to 30 carbon atoms which may have a substituent, R^(a) mayform a ring with the adjacent carbon atom. The formed ring may be eithermonocyclic or polycyclic. The number of carbon atoms (including thecarbon atom bonded thereto) is preferably 5 to 30, and more preferably 5to 20.

Specifically, among the cyclic aliphatic hydrocarbon groups (aliphaticcyclic groups) for R^(a) described above, aliphatic cyclic groups of 5to 30 carbon atoms can be given as examples (provided that the carbonatom bonded thereto is regarded as part of the ring).

It is preferable that R^(a) in the aforementioned formula (C2-3) is ahydrogen atom or a cyclic group which may have a substituent. The cyclicgroup may be either an aromatic hydrocarbon group which may have asubstituent, or an aliphatic cyclic group which may have a substituent.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by formulas (L2) to (L6), (S3) and (S4) are preferable.

As the aromatic hydrocarbon group which may have a substituent, anaphthyl group which may have a substituent, or a phenyl group which mayhave a substituent is preferable.

Examples of the aryl group for R^(b) in the aforementioned formula(C2-3) include the aromatic hydrocarbon groups described above forR^(a), excluding arylalkyl groups. As the aryl group for R^(b), a phenylgroup is more preferable.

The aliphatic cyclic group for R^(b) in the aforementioned formula(C2-3) is the same as defined for the aliphatic cyclic group for R^(a)in the aforementioned formula (C2-3). The aliphatic cyclic group forR^(b) is preferably an aliphatic polycyclic group, more preferably agroup in which one or more hydrogen atoms have been removed from apolycycloalkane, and most preferably a group in which one or morehydrogen atoms have been removed from adamantane.

As the substituent which the aromatic hydrocarbon group or the aliphaticcyclic group for R^(b) may have, the same substituents as thosedescribed above for R^(a) in the aforementioned formula (C2-3) can bementioned.

R^(d) in the aforementioned formula (C2-3) is the same as defined forR^(a) in the aforementioned formula (C2-3).

It is preferable that R^(d) in the aforementioned formula (C2-3) is acyclic group which may have a substituent. The cyclic group may beeither an aromatic hydrocarbon group which may have a substituent, or analiphatic cyclic group which may have a substituent, and an aromaticcyclic group which may have a substituent is preferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by formulas (L2) to (L6), (S3) and (S4) are preferable.

R^(d) in the aforementioned formula (C2-3) is more preferably a naphthylgroup which may have a substituent, or a phenyl group which may have asubstituent, and most preferably a phenyl group which may have asubstituent.

In the formula (C2-3), when both R^(a) and R^(d) represent a hydrocarbongroup of 1 to 30 carbon atoms which may have a substituent, R^(a) andR^(d) are mutually bonded to form a ring. The formed ring may be eithermonocyclic or polycyclic. The number of carbon atoms (including thecarbon atom bonded to R^(a) and R^(d) in the aforementioned formula(C2-3) is preferably 5 to 30, and more preferably 5 to 20.

Specifically, among the cyclic aliphatic hydrocarbon groups (aliphaticcyclic groups) for R^(a) described above, aliphatic cyclic groups of 5to 30 carbon atoms can be given as examples, provided that the carbonatom bonded to R^(a) and R^(d) is regarded as part of the ring.

Specific examples of the component (C23) are shown below.

Further, as a preferable example of the component (C2), the followingcompounds containing an acyloxyimino group (hereafter, sometimesreferred to as “component (C24)”) can also be mentioned.

In the formulae, R¹¹, R¹², R⁴³ and R⁴⁴ each independently represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms; and n7 to n10each independently represents 0 to 3.

Furthermore, as the component (C2), other than the above examples, anyof the known photo-base generators used in conventional chemicallyamplified resist compositions can be used.

Examples of such photo-base generators include ion-type photo-basegenerators (anion-cation complexes); triphenylsulfonium compounds;triphenylmethanol; photoactive carbamates, such as benzylcarbamate andbenzoin carbamate; amides, such as o-carbamoylhydroxylamide,o-carbamoyloxime, aromatic sulfoneamide, alphalactum andN-(2-allylethynyl)amide; oximeesters; α-aminoacetophenone; cobaltcomplexes; and those exemplified in Japanese Unexamined PatentApplication, First Publication No. 2007-279493.

As the component (C2), one type of compound may be used, or two or moretypes of compounds may be used in combination. Among these, as thecomponent (C2), the component (C21) is more preferable.

In the resist composition, the amount of the entire component (C) (thetotal of the component (C1) and the component (C2)), relative to 100parts by weight of the component (A) is preferably from 0.05 to 50 partsby weight, more preferably from 1 to parts by weight, and mostpreferably from 5 to 20 parts by weight.

When the amount of the component (C) is at least as large as the lowerlimit of the above-mentioned range, the film retentiveness of the resistfilm at exposed portions becomes excellent, and the resolution of theformed resist pattern is further improved. On the other hand, when theamount of the component (C) is no more than the upper limit of theabove-mentioned range, the transparency of the resist film can bemaintained.

Acid Supply Component; Component (Z)

In the present invention, in step (1) of the method of forming a resistpattern, a resist composition containing an “acid supply component” as acomponent which supplies acid to the resist film is used.

In the present invention, the “acid supply component” includes acomponent which itself exhibits acidity, i.e., a component which acts asa proton donor (hereafter, referred to as “acidic compound component” or“component (G)”); and a component which is decomposed by heat or light,so as to function as acid (hereafter, referred to as “acid generatorcomponent” or “component (B)”).

Acidic Compound Component (G)

In the present invention, as the component (G), an acidic salt having anacid strength sufficient for increasing the solubility of the component(A) in an alkali developing solution (hereafter, referred to as“component (G1)”) or an acid other than acid salts (acids which do notform a salt, acids which are not ionic; hereafter, referred to as“component (G2)”).

An acid “has an acid strength sufficient for increasing the solubilityof the base component (A) in an alkali developing solution” includesacid, for example, when a polymeric compound (A1) having a structuralunit (a1) is used, by conducting baking (PEB) in step (3), the acid iscapable of causing cleavage of at least part of the bond within thestructure of the acid decomposable group in the structural unit (a1).

[Component (G1)]

Examples of the component (G1) include an ionic compound (salt compound)having a nitrogen-containing cation and a counteranion. The component(G1) itself exhibits acidity even in the form of a salt, and acts as aproton donor.

Hereafter, the cation moiety and the anion moiety of the component (G1)will be described.

(Cation Moiety of Component (G1))

The cation moiety of the component (G1) is not particularly limited aslong as it contains a nitrogen atom. As a preferable example, a cationrepresented by general formula (G1c-1) shown below can be mentioned.

In the formula, R^(101d), R^(101c), R^(101f) and R^(101g) eachindependently represents a hydrogen atom, a linear, branched or cyclicalkyl group, an alkenyl group, an oxoalkyl group or an oxoalkenyl groupof 1 to 12 carbon atoms, an aryl group or an arylalkyl group of 6 to 20carbon atoms, an aralkyl group of 7 to 12 carbon atoms or anaryloxoalkyl group, and part or all of the hydrogen atoms of thesegroups may be substituted with a halogen atom, an alkoxy group or asulfur atom. R^(101d) and R^(101e), or R^(101d), R^(111e) and R^(101f)may be mutually bonded with the nitrogen atom to form a ring, providedthat, when a ring is formed, each of R^(101d) and R^(101c), or each ofR^(101d), R^(101c) and R^(101f) independently represents an alkylenegroup of 3 to 10 carbon atoms, or forms a heterocyclic group containingthe nitrogen atom in the ring thereof.

In formula (G1c-1), R^(101d), R^(101c), R^(101f) and R^(101g)independently represents a hydrogen atom, a linear, branched or cyclicalkyl group, an alkenyl group, an oxoalkyl group or an oxoalkenyl groupof 1 to 12 carbon atoms, an aryl group or an arylalkyl group of 6 to 20carbon atoms, an aralkyl group of 7 to 12 carbon atoms or anaryloxoalkyl group.

As the alkyl group for R^(110d) to R^(101g), the same alkyl groups asthose described above for R¹ and R² can be mentioned, preferably has 1to 10 carbon atoms, and a methyl group, an ethyl group, a propyl groupor a butyl group is particularly desirable.

The alkenyl group for R^(101d) to R^(101g) preferably has 2 to 10 carbonatoms, more preferably 2 to 5, and still more preferably 2 to 4.Specific examples thereof include a vinyl group, a propenyl group (anallyl group), a butynyl group, a 1-methylpropenyl group and a2-methylpropenyl group.

The oxoalkyl group for R^(101d) to R^(101g) preferably has 2 to 10carbon atoms, and examples thereof include a 2-oxoethyl group, a2-oxopropyl group, a 2-oxocyclopentyl group and a 2-oxocyclohexyl group.

Examples of the oxoalkenyl group for R^(101d) to R^(101g) include anoxo-4-cyclohexenyl group and a 2-oxo-4-propenyl group.

As the aryl group for R^(101d) to R^(101g), the same aryl groups asthose described above as the aromatic hydrocarbon group for R¹ and R²can be mentioned, and a phenyl group or a naphthyl group is preferable.Examples of the arylalkyl group include aryl groups in which one or morehydrogen atoms have been substituted with an alkyl group (preferably analkyl group of 1 to 5 carbon atoms).

Examples of the aralkyl group and aryloxoalkyl group for R^(101d) toR^(110g) include a benzyl group, a phenylethyl group, a phenethyl group,a 2-phenyl-2-oxoethyl group, a 2-(1-naphthyl)-2-oxoethyl group and a2-(2-naphthyl)-2-oxoethyl group.

The hydrogen atoms within the alkyl group, the alkenyl group, theoxoalkyl group, the oxoalkenyl group, the aryl group, the arylalkylgroup, the aralkyl group and the aryloxoalkyl group for R^(101d) toR^(101g) may or may not be substituted with a halogen atom such as afluorine atom, an alkoxy group or a sulfur atom.

When R^(101d) to R^(101g) are constituted of only a combination of alkylgroups and hydrogen atoms, in terms of storage stability and lithographyproperties, it is preferable that part of the hydrogen atoms of thealkyl group is substituted with a halogen atom such as a fluorine atom,an alkoxy group or a sulfur atom.

Further, R^(101d) and R^(101e), or R^(101d), R^(101e) and R^(101f) maybe mutually bonded to form a ring with the nitrogen atom. Examples ofthe formed ring include a piperidine ring, a hexamethylene imine ring,an azole ring, a pyridine ring, a pyrimidine ring, an azepine ring, apyrazine ring, a quinoline ring and a benzoquinoline ring.

Further, the ring may contain an oxygen atom in the ring skeletonthereof, and specific examples of preferable rings which contain anoxygen atom include an oxazole ring and an isooxazole ring.

Among these examples, as the cation moiety represented by theaforementioned formula (G1c-1), a nitrogen-containing cation having apKa of 7 or less is preferable.

In the present invention, pKa refers to an acid dissociation constantwhich is generally used as a parameter which shows the acid strength ofan objective substance. The pKa value of the cation of the component(G1) can be determined by a conventional method. Alternatively, the pKavalue can be estimated by calculation using a conventional software suchas “ACD/Labs” (trade name; manufactured by Advanced ChemistryDevelopment, Inc.).

The pKa of the component (G1) is preferably 7 or less, and the “acidsalt” can be appropriately selected depending on the type and pKa of thecounteranion, so that is becomes a weak base relative to thecounteranion. Specifically, the pKa of the cation of the “acid salt” ispreferably from −2 to 7, more preferably from −1 to 6.5, and still morepreferably 0 to 6. When the pKa is no more than the upper limit of theabove-mentioned range, the basicity of the cation can be renderedsatisfactorily weak, and the component (G1) itself becomes an acidiccompound. Further, when the pKa is at least as large as the lower limitof the above-mentioned range, a salt can be more reliably formed withthe counteranion, and it becomes possible to appropriately control theacidity of the component (G1), thereby preventing deterioration of thestorage stability caused by the component (G1) being excessively acidic.

As a cation which satisfies the above pKa, a cation represented by anyone of the following general formulae (G1c-11) to (G1c-13) isparticularly desirable.

In the formulae, Rf^(g1) represents a fluorinated alkyl group of 1 to 12carbon atoms; Rn^(g1) and Rn^(g2) each independently represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms, provided thatRn^(g1) and R^(g2) may be mutually bonded to form a ring; Q^(a) to Q^(c)each independently represents a carbon atom or a nitrogen atom; Rn^(g3)represents a hydrogen atom or a methyl group; Rn^(g4) and Rn^(g5) eachindependently represents an alkyl group of 1 to 5 carbon atoms or anaromatic hydrocarbon group; R^(g1) and R^(g2) each independentlyrepresents a hydrocarbon group; and n15 and n16 each independentlyrepresents an integer of 0 to 4, provided that, when n15 and n16 is 2 ormore, the plurality of R^(g1) and R^(g2) which substitute the hydrogenatoms of the adjacent carbon atom may be bonded to form a ring.

In formula (G1c-11), Rf^(g1) represents a fluorinated alkyl group of 1to 12 carbon atoms, and is preferably a fluorinated alkyl group of 1 to5 carbon atoms in which 50% or more of the hydrogen atoms of the alkylgroup have been fluorinated.

In formula (G1c-13), Rn^(g4) and Rn^(g5) each independently representsan alkyl group of 1 to 5 carbon atoms or an aromatic hydrocarbon group,and is the same as defined for the alkyl group of 1 to 5 carbon atomsand aryl groups as those described above in the explanation of R^(101d),R^(101e), R^(101f) and R^(101g) in formula (G1c-1).

In formulae (G1c-12) and (G1c-13), n15 and n16 each independentlyrepresents an integer of 0 to 4, preferably an integer of 0 to 2, andmore preferably 0.

In formulae (G1c-12) and (G1c-13), R^(g1) and R^(g2) each independentlyrepresents a hydrocarbon group, and is preferably an alkyl group oralkenyl group of 1 to 12 carbon atoms. The alkyl group and the alkenylgroup are the same as defined for those described in the explanation offormula (G1c-1).

When n15 and n16 are 2 or more, the plurality of R^(g) and R^(g2) may bethe same or different from each other. Further, when n15 and n16 is 2 ormore, the plurality of R^(g1) and R^(g2) which substitute the hydrogenatoms of the adjacent carbon atom may be bonded to form a ring. Examplesof the formed ring include a benzene ring and a naphthalene ring. Thatis, the compound represented by formula (G1c-12) or (G1c-13) may be acondensed ring compound formed by condensation of 2 or more rings.

Specific examples of compounds represented by any one of theaforementioned formulae (G1c-11) to (G1c-13) are shown below.

(Anion Moiety of Component (G1))

The anion moiety of the component (G1) is not particularly limited, andany of those generally used the anion moiety of a salt used in a resistcomposition may be appropriately selected for use.

Among these, as the anion moiety of the component (G1), those whichforms a salt with the aforementioned cation moiety for the component(G1) to form a component (G1) that is capable of increasing thesolubility of the component (A) in an alkali developing solution ispreferable.

The acid salt “capable of increasing the solubility of the component (A)in an alkali developing solution” refers to an acid salt, for example,when a component (A1) having a structural unit (a1) is used, byconducting baking in the aforementioned step (3), the acid salt iscapable of causing cleavage of at least part of the bond within thestructure of the acid decomposable group in the structural unit (a1).

That is, the anion moiety of the component (G1) preferably has a strongacidity. Specifically, the pKa of the anion moiety is more preferably 0or less, still more preferably −15 to −1, and most preferably −13 to −3.When the pKa of the anion moiety is no more than 0, the acidity of theanion can be rendered satisfactorily strong relative to a cation havinga pKa of 7 or less, and the component (G1) itself becomes an acidiccompound. On the other hand, when the pKa of the anion moiety is −15 ormore, deterioration of the storage stability caused by the component(G1) being excessively acidic can be prevented.

As the anion moiety of the component (G1), an anion moiety having atleast one anion group selected from a sulfonate anion, a carboxylateanion, a sulfonylimide anion, a bis(alkylsulfonyl)imide anion and atris(alkylsulfonyl)methide anion is preferable.

Specific examples include anions represented by general formula: “R⁴″SO₃⁻ (R⁴″ represents a linear, branched or cyclic alkyl group which mayhave a substituent, a halogenated alkyl group, an aryl group or analkenyl group)”.

In the aforementioned general formula “R⁴″SO₃ ⁻”, R⁴″ represents alinear, branched or cyclic alkyl group which may have a substituent, ahalogenated alkyl group, an aryl group or an alkenyl group.

The linear or branched alkyl group for the aforementioned R⁴″ preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 4.

The cyclic alkyl group for the aforementioned R⁴″ preferably has 4 to 15carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably6 to 10 carbon atoms.

When R⁴″ represents an alkyl group, examples of “R⁴″SO₃ ⁻” includealkylsulfonates, such as methanesulfonate, n-propanesulfonate,n-butanesulfonate, n-octanesulfonate, 1-adamantanesulfonate,2-norbornanesulfonate and d-camphor-10-sulfonate.

The halogenated alkyl group for the aforementioned R⁴″ is an alkyl groupin which part or all of the hydrogen atoms thereof have been substitutedwith a halogen atom. The alkyl group preferably has 1 to 5 carbon atoms,and is preferably a linear or branched alkyl group, and more preferablya methyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, a tert-butyl group, a tert-pentyl group or an isopentylgroup. Examples of the halogen atom which substitutes the hydrogen atomsinclude a fluorine atom, a chlorine atom, an iodine atom and a bromineatom.

In the halogenated alkyl group, it is preferable that 50 to 100% of allhydrogen atoms within the alkyl group (prior to halogenation) have beensubstituted with a halogen atom, and it is preferable that all hydrogenatoms have been substituted with a halogen atom.

As the halogenated alkyl group, a fluorinated alkyl group is preferable.The fluorinated alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.

Further, the fluorination ratio of the fluorinated alkyl group ispreferably from to 100%, more preferably from 50 to 100%, and it is mostpreferable that all hydrogen atoms are substituted with fluorine atomsbecause the acid strength increases.

Specific examples of such fluorinated alkyl groups include atrifluoromethyl group, a heptafluoro-n-propyl group and anonafluoro-n-butyl group.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means thatpart of or all of the hydrogen atoms within the aforementioned linear,branched or cyclic alkyl group, halogenated alkyl group, aryl group oralkenyl group may be substituted with substituents (atoms other thanhydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group, and a group represented by the formula X³-Q′— (in theformula, Q′ represents a divalent linking group containing an oxygenatom; and X³ represents a hydrocarbon group of 3 to 30 carbon atomswhich may have a substituent).

Examples of halogen atoms and alkyl groups include the same halogenatoms and alkyl groups as those described above with respect to thehalogenated alkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and asulfur atom.

In the group represented by formula X³-Q′—, Q′ represents a divalentlinking group containing an oxygen atom.

Q′ may contain an atom other than an oxygen atom. Examples of atomsother than oxygen include a carbon atom, a hydrogen atom, a sulfur atomand a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond(—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate bond(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,hetero atom-containing linking groups with an alkylene group.Furthermore, the combinations may have a sulfonyl group (—SO₂—) bondedthereto.

Specific examples of such combinations include —R⁹¹—O—, —R⁹²—O—C(═O)—,—C(═O)—O—R⁹³—O—C(═O)—, —SO₂—O—R⁹⁴—O—C(═O)—, and —R⁹⁵—SO₂—O—R⁹⁴—O—C(═O)—(in the formula, R⁹¹ to R⁹⁵ independently represents an alkylene group).

The alkylene group for R⁹¹ to R⁹⁵ is preferably a linear or branchedalkylene group, and preferably has 1 to 12 carbon atoms, more preferably1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; a trimethylene group(n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylene groups such as—CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylene group[—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

As Q′, a divalent linking group containing an ester bond or an etherbond is preferable, and —R¹⁹—O—, —R⁹²—O—C(═O)— or —C(═O)—O—R⁹³—O—C(═O)—is more preferable.

In the group represented by the formula: X³-Q′—, the hydrocarbon groupfor X³ is the same as the hydrocarbon groups of 1 to 30 carbon atoms forR^(a) in the aforementioned formula (C3).

Among these, as X³, a linear alkyl group which may have a substituent,or a cyclic group which may have a substituent is preferable. The cyclicgroup may be either an aromatic hydrocarbon group which may have asubstituent, or an aliphatic cyclic group which may have a substituent,and an aliphatic cyclic group which may have a substituent ispreferable.

As the aromatic hydrocarbon group, a naphthyl group which may have asubstituent, or a phenyl group which may have a substituent ispreferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, or any oneof groups represented by the aforementioned formulae (L2) to (L6), (S3)and (S4) are preferable.

Among these examples, as the aforementioned R⁴″, a halogenated alkylgroup or a group having X³-Q′— as a substituent is preferable.

When the R⁴″ group has X³-Q′— as a substituent, as R⁴″, a grouprepresented by the formula: X³-Q′—Y³— (in the formula, Q′ and X³ are thesame as defined above, and Y³ represents an alkylene group of 1 to 4carbon atoms which may have a substituent or a fluorinated alkylenegroup of 1 to 4 carbon atoms which may have a substituent is preferable.

In the group represented by the formula X³-Q′—Y³—, as the alkylene groupfor Y³, the same alkylene group as those described above for Q′ in whichthe number of carbon atoms is 1 to 4 can be used.

As the fluorinated alkylene group, the aforementioned alkylene group inwhich part or all of the hydrogen atoms has been substituted withfluorine atoms can be used. Specific examples of Y³ include —CF₂—,—CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—, —CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—,—CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—,—C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—,—CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—, —C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—,—CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —CH₂CH₂CH₂CH₂—,—CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—,—CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and —C(CH₃)(CH₂CH₃)—.

Y³ is preferably a fluorinated alkylene group, and most preferably afluorinated alkylene group in which the carbon atom bonded to theadjacent sulfur atom is fluorinated. Examples of such fluorinatedalkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—;—CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable,—CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— isparticularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group has been substituted withgroups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

Specific examples of groups represented by formula R⁴″SO³⁻ in which R⁴″represents X₃ ^(Q′—Y-3) include anions represented by the followingformulae (b1) to (b9).

In the formulae, q1 and q2 each independently represents an integer of 1to 5; q3 represents an integer of 1 to 12; t3 represents an integer of 1to 3; r1 and r2 each independently represents an integer of 0 to 3; irepresents an integer of 1 to 20; R⁷ represents a substituent; n1 to n6each independently represents 0 or 1; v0 to v6 each independentlyrepresents an integer of 0 to 3; w1 to w6 each independently representsan integer of 0 to 3; and Q″ is the same as defined above.

As the substituent for R⁷, the same groups as those which theaforementioned aliphatic hydrocarbon group or aromatic hydrocarbon groupfor R^(a) in the aforementioned formula (C3) may have as a substituentcan be used.

If there are two or more of the R⁷ group, as indicated by the values r1,r2, and w1 to w6, then the two or more of the R⁷ groups may be the sameor different from each other.

Further, as preferable examples of the anion moiety of the component(G1), an anion represented by general formula (G1a-3) shown below and ananion moiety represented by general formula (G1a-4) shown below can alsobe mentioned.

In the formulas, X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom; and each of Y″ and Z″ independently represents an alkyl group of 1to 10 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom.

In formula (G1a-3), X″ represents a linear or branched alkylene group inwhich at least one hydrogen atom has been substituted with a fluorineatom, and the alkylene group preferably has 2 to 6 carbon atoms, morepreferably 3 to 5 carbon atoms, and most preferably 3 carbon atoms.

In formula (G1a-4), each of Y″ and Z″ independently represents a linearor branched alkyl group in which at least one hydrogen atom has beensubstituted with a fluorine atom, and the alkyl group preferably has 1to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and mostpreferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in a resistsolvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved.

The amount of fluorine atoms within the alkylene group or alkyl group,i.e., fluorination ratio, is preferably from 70 to 100%, more preferablyfrom 90 to 100%, and it is particularly desirable that the alkylenegroup or alkyl group be a perfluoroalkylene or perfluoroalkyl group inwhich all hydrogen atoms are substituted with fluorine atoms.

As the anion moiety of the component (G1), an anion represented by theaforementioned formula “R⁴″SO₃ ⁻” (in particular, any one of anionsrepresented by the aforementioned formulae (b1) to (b9) which is a groupin which R⁴″ is “X³-Q′—Y³—”) or an anion represented by theaforementioned formula (G1a-3) is most preferable.

As the component (G1), one type of compound may be used alone, or two ormore types may be used in combination.

In the resist composition, the amount of the component (G1) within thecomponent (G) is preferably 40% by weight or more, still more preferably70% by weight or more, and may be even 100% by weight. When the amountof the component (G1) is at least as large as the lower limit of theabove-mentioned range, the storage stability and the lithographyproperties become excellent.

In the resist composition, the amount of the component (G1), relative to100 parts by weight of the component (A) is preferably from 0.5 to 30parts by weight, more preferably from 1 to 20 parts by weight, and mostpreferably from 2 to 15 parts by weight. When the amount of thecomponent (G1) is within the above-mentioned range, the lithographyproperties become excellent.

[Component (G2)]

The component (G2) is a component which does not fall under thedefinition of the component (G1), and the component (G2) itself exhibitsacidity, so as to act as a proton donor. Examples of the component (G2)include a non-ionic acid which does not form a salt.

As the component (G2), there is no particular limitation as long as itis an acid exhibiting an acid strength sufficient for increasing thesolubility of the base component (A) in an alkali developing solution.As the component (G2), in terms of the reactivity with the aciddissociable group of the base component and ease in increasing thesolubility of the resist film in an alkali developing solution, an imineacid or a sulfonic acid compound is preferable, and examples thereofinclude sulfonylimide, bis(alkylsulfonyl)imide,tris(alkylsulfonyl)methide, and any of these compounds which have afluorine atom.

In particular, a compound represented by any one of general formulae(G2-1) to (G2-3) shown below (preferably a compound represented bygeneral formula (G2-2)), a compound in which an anion represented by anyone of general formulae (b1) to (b8) described above has “—SO₃ ⁻”replaced by “—SO₃H”, a compound in which an anion represented by generalformula (G1a-3) or (G1a-4) described above has “N” replaced by “NH”, andcamphorsulfonic acid are preferable. Other examples include acidcomponents such as a fluorinated alkyl group-containing carboxylic acid,a higher fatty acid, a higher alkylsulfonic acid, and a higheralkylarylsulfonic acid.

In formula (G2-1), w′ represents an integer of 1 to 5. In formula(G2-2), R^(f) represents a hydrogen atom or an alkyl group (providedthat part or all of the hydrogen atoms within the alkyl group may besubstituted with a fluorine atom, a hydroxy group, an alkoxy group, acarboxy group or an amino group); and y′ represents 2 or 3. In formula(G2-3), R^(f) is the same as defined above; and z′ represents 2 or 3.

Examples of compounds represented by the aforementioned formula (G2-1)include (C₄F₉SO₂)₂NH and (C₃F₇SO₂)₂NH.

In the aforementioned formula (G2-2), the alkyl group for R^(f)preferably has 1 or 2 carbon atoms, and more preferably 1.

Examples of the alkoxy group which may substitute the hydrogen atom(s)within the alkyl group include a methoxy group and an ethoxy group.

Examples of a compound represented by the aforementioned formula (G2-2)include a compound represented by a chemical formula (G2-21) shownbelow.

In the aforementioned formula (G2-3), R^(f) is the same as defined forR^(f) in formula (G2-2).

Examples of a compound represented by the aforementioned formula (G2-3)include a compound represented by a chemical formula (G2-31) shownbelow.

As the fluorinated alkyl group-containing carboxylic group, for example,C₁₀F₂₁COOH can be mentioned.

Examples of the higher fatty acid include higher fatty acids having analkyl group of 8 to 20 carbon atoms, and specific examples thereofinclude dodecanoic acid, tetradecanoic acid, and stearic acid.

The alkyl group of 8 to 20 carbon atoms may be either linear orbranched. Further, the alkyl group of 8 to 20 carbon atoms may have aphenylene group, an oxygen atom or the like interposed within the chainthereof. Furthermore, the alkyl group of 8 to 20 carbon atoms may havepart of the hydrogen atoms substituted with a hydroxy group or a carboxygroup.

Examples of the higher alkylsulfonic acid include sulfonic acids havingan alkyl group preferably with an average of 9 to 21 carbon atoms, morepreferably 12 to 18 carbon atoms, and specific examples thereof includedecanesulfonic acid, dodecanesulfonic acid, tetradecanesulfonic acid,tetradecanesulfonic acid, pentadecanesulfonic acid andoctadecanesulfonic acid.

Examples of the higher alkylarylsulfonic acid includealkylbenzenesulfonic acids and alkylnaphthalenesulfonic acids having analkyl group preferably with an average of 6 to 18 carbon atoms, morepreferably 9 to 15 carbon atoms, and specific examples thereof includedodecylbenzenesulfonic acid and decylnaphthalenesulfonic acid.

Examples of the acid components include alkyldiphenyletherdisulfonicacids preferably with an average of 6 to 18 carbon atoms, morepreferably 9 to 15, and preferable examples thereof includedodecyldiphenyletherdisulfonic acid.

Examples of the component (G2) other than those described above includeorganic carboxylic acid, a phosphorus oxo acid or derivative thereof.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

When the component (G) includes a component (G2), as the component (G2),one type of compound may be used, or two or more types may be used incombination. Among these, as the component (G2), at least one memberselected from the group consisting of sulfonylimide,bis(alkylsulfonyl)imide, tris(alkylsulfonyl)methide and any of thesecompounds having a fluorine atom is preferable, and it is mostpreferable to use at least one of these compounds having a fluorineatom.

Further, when the resist composition contains the component (G2), theamount of the component (G2) relative to 100 parts by weight of thecomponent (A) is preferably within a range from 0.5 to 20 parts byweight, more preferably from 1 to 15 parts by weight, and still morepreferably from 1 to 10 parts by weight. When the amount of thecomponent (G2) is at least as large as the lower limit of theabove-mentioned range, the solubility of the resist film in an alkalideveloping solution is likely to be increased. On the other hand, whenthe amount of the component (G2) is no more than the upper limit of theabove-mentioned range, an excellent sensitivity can be obtained.

Acid Generator Component; Component (B)

In the present invention, as the acid supply component (Z), an acidgenerator component (hereafter, sometimes referred to as “component(B)”) which is decomposed by heat or exposure, so as to function as acidcan also be used.

Differing from the component (G), the component (B) generates acid uponexposure in step (2) and upon baking (PEB) in step (3). The component(B) itself does not need to exhibit acidity.

As the component (B), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used.

As the acid generator, a thermal acid generator which generates acidupon heating and a photoacid generator which generates acid uponexposure can be mentioned. Examples of such acid generators arenumerous, and include onium salt acid generators such as iodonium saltsand sulfonium salts; oxime sulfonate acid generators; diazomethane acidgenerators such as bisalkyl or bisaryl sulfonyl diazomethanes andpoly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate acid generators;iminosulfonate acid generators; and disulfone acid generators.

These acid generator components are generally known as photoacidgenerators (PAG), but also function as thermal acid generators (TAG).Therefore, the acid generator component usable in the present inventioncan be appropriately selected from those which have been conventionallyknown as acid generators for chemically amplified resist compositions.

A “thermal acid generator which generates acid upon heating” refers to acomponent which generates acid upon heating preferably at a PEBtemperature or lower in step (3), i.e., 200° C. or lower, and morepreferably at 50 to 150° C. By selecting a component which generatesacid with a heating temperature of PEB temperature or lower, theoperations becomes easy. Further, it becomes possible to control thegeneration of acid from the thermal acid generator and the deprotectionreaction of the base component at different temperatures. Morepreferably, by selecting a component which generates acid at 50° C. orhigher, the stability in the resist composition becomes excellent.

As the onium salt acid generator for the component (B), those in whichhave at least one anion group selected from a sulfonate anion, acarboxylate anion, a sulfonylimide anion, a bis(alkylsulfonyl)imideanion and a tris(alkylsulfonyl)methide anion within the anion moiety ispreferable. More specifically, the same anion moieties as thosedescribed above for the component (G1) can be mentioned.

Further, as the cation moiety, a cation moiety represented by generalformula (b-c1) or (b-c2) shown below is preferable.

In the formulae, R¹″ to R³″, R⁵″ and R⁶″ each independently representsan aryl group which may have a substituent, an alkyl group which mayhave a substituent or an alkenyl group which may have a substituent,provided that, in formula (b-c1), two of R¹″ to R³″ may be mutuallybonded to form a ring with the sulfur atom; and

In formula (b-c1), R¹″ to R³″ each independently represents an arylgroup which may have a substituent or an alkyl group which may have asubstituent. Two of R¹″ to R³″ may be mutually bonded to form a ringwith the sulfur atom.

Examples of the aryl group for R¹″ to R³″ include an unsubstituted arylgroup of 6 to 20 carbon atoms; a substituted aryl group in which part orall of the hydrogen atoms of the aforementioned unsubstituted aryl grouphas been substituted with an alkyl group, an alkoxy group, a halogenatom, a hydroxy group, an oxo group (═O), an aryl group, analkoxyalkyloxy group, an alkoxycarbonylalkyloxy group, —C(═O)—O—R⁶′,—O—C(═O)—R⁷′ or —O—R⁸′. Each of R⁶′, R⁷′ and R⁸′ independentlyrepresents a linear or branched saturated hydrocarbon group of 1 to 25atoms, a cyclic saturated hydrocarbon group of 3 to 20 carbon atoms or alinear or branched, aliphatic unsaturated hydrocarbon group of 2 to 5carbon atoms.

The unsubstituted aryl group for R¹″ to R³″ is preferably an aryl grouphaving 6 to 10 carbon atoms because it can be synthesized at a low cost.Specific examples thereof include a phenyl group and a naphthyl group.

The alkyl group as the substituent for the substituted aryl grouprepresented by R¹″ to R³″ is preferably an alkyl group having 1 to 5carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent for the substituted aryl group ispreferably an alkoxy group having 1 to 5 carbon atoms, and a methoxygroup, an ethoxy group, an n-propoxy group, an iso-propoxy group, ann-butoxy group or a tert-butoxy group is particularly desirable.

The halogen atom as the substituent for the substituted aryl group ispreferably a fluorine atom.

As the aryl group as the substituent for the substituted aryl group, thesame aryl groups as those described for R¹″ to R³″ can be mentioned.

Examples of alkoxyalkyloxy groups as the substituent for the substitutedaryl group include groups represented by a general formula shown below:

—O—C(R⁴⁷)(R⁴⁸)—O—R⁴⁹

In the formula, R⁴⁷ and R⁴⁸ each independently represents a hydrogenatom or a linear or branched alkyl group; and R⁴⁹ represents an alkylgroup.

The alkyl group for R⁴⁷ and R⁴⁸ preferably has 1 to 5 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is preferable that at least one of R⁴⁷ and R⁴⁸ be a hydrogen atom. Itis particularly desirable that at least one of R⁴⁷ and R⁴⁸ be a hydrogenatom, and the other be a hydrogen atom or a methyl group.

The alkyl group for R⁴⁹ preferably has 1 to 15 carbon atoms, and may belinear, branched or cyclic.

The linear or branched alkyl group for R⁴⁹ preferably has 1 to 5 carbonatoms. Examples thereof include a methyl group, an ethyl group, a propylgroup, an n-butyl group and a tert-butyl group.

The cyclic alkyl group for R⁴⁹ preferably has 4 to 15 carbon atoms, morepreferably 4 to 12, and most preferably 5 to 10. Specific examplesthereof include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane or a polycycloalkane such as abicycloalkane, tricycloalkane or tetracycloalkane, and which may or maynot be substituted with an alkyl group of 1 to 5 carbon atoms, afluorine atom or a fluorinated alkyl group. Examples of themonocycloalkane include cyclopentane and cyclohexane. Examples ofpolycycloalkanes include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

Examples of the alkoxycarbonylalkyloxy group as the substituent for thesubstituted aryl group include groups represented by a general formulashown below:

—O—R⁵⁰—C(═O)—O—R⁵⁶

In the formula, R⁵⁰ represents a linear or branched alkylene group, andR⁵⁶ represents a tertiary alkyl group.

The linear or branched alkylene group for R⁵⁰ preferably has 1 to 5carbon atoms, and examples thereof include a methylene group, anethylene group, a trimethylene group, a tetramethylene group and a1,1-dimethylethylene group.

Examples of the tertiary alkyl group for R⁵⁶ include a2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group, a1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a1-methyl-1-cyclohexyl group, a 1-ethyl-1-cyclohexyl group, a1-(1-adamantyl)-1-methylethyl group, a 1-(1-adamantyl)-1-methylpropylgroup, a 1-(1-adamantyl)-1-methylbutyl group, a1-(1-adamantyl)-1-methylpentyl group, a 1-(1-cyclopentyl)-1-methylethylgroup, a 1-(1-cyclopentyl)-1-methylpropyl group, a1-(1-cyclopentyl)-1-methylbutyl group, a1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethylgroup, a 1-(1-cyclohexyl)-1-methylpropyl group, a1-(1-cyclohexyl)-1-methylbutyl group, a 1-(1-cyclohexyl)-1-methylpentylgroup, a tert-butyl group, a tert-pentyl group and a tert-hexyl group.

Further, a group in which R⁵⁶ in the group represented by theaforementioned general formula: —O—R⁵⁰—C(═O)—O—R⁵⁶ has been substitutedwith R⁵⁶′ can also be mentioned. R⁵⁶′ represents a hydrogen atom, analkyl group, a fluorinated alkyl group or an aliphatic cyclic groupwhich may contain a hetero atom.

The alkyl group for R⁵⁶′ is the same as defined for the alkyl group forthe aforementioned R⁴⁹.

Examples of the fluorinated alkyl group for R⁵⁶′ include groups in whichpart or all of the hydrogen atoms within the alkyl group for R⁴⁹ hasbeen substituted with a fluorine atom.

Examples of the aliphatic cyclic group for R⁵⁶′ which may contain ahetero atom include an aliphatic cyclic group which does not contain ahetero atom, an aliphatic cyclic group containing a hetero atom in thering structure, and an aliphatic cyclic group in which a hydrogen atomhas been substituted with a hetero atom.

As an aliphatic cyclic group for R⁵⁶′ which does not contain a heteroatom, a group in which one or more hydrogen atoms have been removed froma monocycloalkane or a polycycloalkane such as a bicycloalkane, atricycloalkane or a tetracycloalkane can be mentioned. Examples of themonocycloalkane include cyclopentane and cyclohexane. Examples ofpolycycloalkanes include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

Specific examples of the aliphatic cyclic group for R⁵⁶′ containing ahetero atom in the ring structure include groups represented by theaforementioned formulae (L1) to (L6) and (S1) to (S4).

As the aliphatic cyclic group for R⁵⁶′ in which a hydrogen atom has beensubstituted with a hetero atom, an aliphatic cyclic group in which ahydrogen atom has been substituted with an oxygen atom (═O) can bementioned.

In formulae —C(═O)—O—R⁶′, —O—C(═O)—R⁷′ and —O—R⁸′, R⁶′, R⁷′ and R⁸′ eachindependently represents a linear or branched saturated hydrocarbongroup of 1 to 25 atoms, a cyclic saturated hydrocarbon group of 3 to 20carbon atoms or a linear or branched, aliphatic unsaturated hydrocarbongroup of 2 to 5 carbon atoms.

The linear or branched, saturated hydrocarbon group preferably has 1 to25 carbon atoms, more preferably 1 to 15, and still more preferably 4 to10.

Examples of the linear, saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group and a decylgroup.

Examples of the branched, saturated hydrocarbon group include a1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group and a 4-methylpentyl group,but excluding tertiary alkyl groups.

The linear or branched, saturated hydrocarbon group may have asubstituent. Examples of the substituent include an alkoxy group, ahalogen atom, a halogenated alkyl group, a hydroxyl group, an oxygenatom (═O), a cyano group and a carboxy group.

The alkoxy group as the substituent for the linear or branched saturatedhydrocarbon group is preferably an alkoxy group having 1 to 5 carbonatoms, more preferably a methoxy group, an ethoxy group, an n-propoxygroup, an iso-propoxy group, an n-butoxy group or a tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the linear orbranched, saturated alkyl group include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the halogenated alkyl group as the substituent for the linearor branched, saturated hydrocarbon group includes a group in which partor all of the hydrogen atoms within the aforementioned linear orbranched, saturated hydrocarbon group have been substituted with theaforementioned halogen atoms.

The cyclic saturated hydrocarbon group of 3 to 20 carbon atoms for R⁶′,R⁷′ and R⁸′ may be either a polycyclic group or a monocyclic group, andexamples thereof include groups in which one hydrogen atom has beenremoved from a monocycloalkane, and groups in which one hydrogen atomhas been removed from a polycycloalkane (e.g., a bicycloalkane, atricycloalkane or a tetracycloalkane). More specific examples includegroups in which one hydrogen atom has been removed from amonocycloalkane such as cyclopentane, cyclohexane, cycloheptane orcyclooctane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

The cyclic, saturated hydrocarbon group may have a substituent. Forexample, part of the carbon atoms constituting the ring within thecyclic alkyl group may be substituted with a hetero atom, or a hydrogenatom bonded to the ring within the cyclic alkyl group may be substitutedwith a substituent.

In the former example, a heterocycloalkane in which part of the carbonatoms constituting the ring within the aforementioned monocycloalkane orpolycycloalkane has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom, and one hydrogen atom hasbeen removed therefrom, can be used. Further, the ring may contain anester bond (—C(═O)—O—). More specific examples include alactone-containing monocyclic group, such as a group in which onehydrogen atom has been removed from γ-butyrolactone; and alactone-containing polycyclic group, such as a group in which onehydrogen atom has been removed from a bicycloalkane, tricycloalkane ortetracycloalkane containing a lactone ring.

In the latter example, as the substituent, the same substituent groupsas those for the aforementioned linear or branched alkyl group, or alower alkyl group can be used.

Alternatively, R⁶′, R⁷′ and R⁸′ may be a combination of a linear orbranched alkyl group and a cyclic group.

Examples of the combination of a linear or branched alkyl group with acyclic alkyl group include groups in which a cyclic alkyl group as asubstituent is bonded to a linear or branched alkyl group, and groups inwhich a linear or branched alkyl group as a substituent is bonded to acyclic alkyl group.

Examples of the linear aliphatic unsaturated hydrocarbon group for R⁶′,R⁷′ and R⁸′ include a vinyl group, a propenyl group (an allyl group) anda butynyl group.

Examples of the branched aliphatic unsaturated hydrocarbon group forR⁶′, R⁷′ and R⁸′ include a 1-methylpropenyl group and a 2-methylpropenylgroup.

The aforementioned linear or branched, aliphatic unsaturated hydrocarbongroup may have a substituent. Examples of substituents include the samesubstituents as those which the aforementioned linear or branched alkylgroup may have.

Among the aforementioned examples, as R⁷′ and R⁸′, in terms ofimprovement in lithography properties and shape of the resist pattern, alinear or branched, saturated hydrocarbon group of 1 to 15 carbon atomsor a cyclic saturated hydrocarbon group of 3 to 20 carbon atoms ispreferable.

Examples of the alkyl group for R¹″ to R³″ include linear, branched orcyclic alkyl groups of 1 to 10 carbon atoms. Among these, alkyl groupsof 1 to 5 carbon atoms are preferable as the resolution becomesexcellent. Specific examples thereof include a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, acyclohexyl group, a nonyl group, and a decyl group, and a methyl groupis most preferable because it is excellent in resolution and can besynthesized at a low cost.

The alkenyl group for R¹″ to R³″ preferably has 2 to 10 carbon atoms,more preferably 2 to 5, and still more preferably 2 to 4. Specificexamples thereof include a vinyl group, a propenyl group (an allylgroup), a butynyl group, a 1-methylpropenyl group and a 2-methylpropenylgroup.

When two of R¹″ to R³″ are bonded to each other to form a ring with thesulfur atom, it is preferable that the two of R¹″ to R³″ form a 3 to10-membered ring including the sulfur atom, and it is particularlydesirable that the two of R¹″ to R³″ form a 5 to 7-membered ringincluding the sulfur atom.

Preferable examples of the cation moiety of the compound represented bythe aforementioned formula (b-c1) are shown below.

In the formula, g1 represents a recurring number, and is an integer of 1to 5.

In the formula, g2 and g3 represent recurring numbers, wherein g2 is aninteger of 0 to 20, and g3 is an integer of 0 to 20.

In the formula, R^(C) represents a substituent described above in theexplanation of the aforementioned substituted aryl group (an alkylgroup, an alkoxy group, an alkoxyalkyloxy group, analkoxycarbonylalkyloxy group, a halogen atom, a hydroxy group, an oxogroup (═O), an aryl group, —C(═O)—O—R⁶′, —O—C(═O)—R⁷′, and —O—R⁸′).

In formula (b-c2), R⁵″ and R⁶″ each independently represents an arylgroup which may have a substituent or an alkyl group which may have asubstituent.

As the aryl group for R⁵″ and R⁶″, the same aryl groups as thosedescribed above for R¹″ to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same alkyl groups as thosedescribed above for R¹″ to R³″ can be used.

As the alkenyl group for R⁵″ and R⁶″, the same as the alkenyl groups forR¹″ to R³″ can be used.

Specific examples of the cation moiety of the compound represented bygeneral formula (b-c2) include diphenyliodonium andbis(4-tert-butylphenyl)iodonium.

In the present description, an oximesulfonate acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

In the formula, each of R³¹ and R³² independently represents an organicgroup.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The alkyl group or the aryl group “hasa substituent” means that part or all of the hydrogen atoms of the alkylgroup or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which part of the hydrogen atoms aresubstituted with halogen atoms and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of halogen atoms includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable. In other words, thehalogenated alkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² include the same alkyl groups and aryl groupsas those described above for R³¹

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andmost preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.Further, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), as the alkyl group having no substituent andthe halogenated alkyl group for R³⁶, the same alkyl group having nosubstituent and the halogenated alkyl group described above for R³³ canbe used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate acid generators includeα-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate acid generators disclosed in WO 2004/074242A2 (Examples1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane acid generators, specific examples ofsuitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 11-035551, JapaneseUnexamined Patent Application, First Publication No. Hei 11-035552 andJapanese Unexamined Patent Application, First Publication No. Hei11-035573 may be preferably used.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

As the component (B), one type of these acid generators may be usedalone, or two or more types may be used in combination.

In the case where the resist composition contains the component (B),when the component (B) is a thermal acid generator, the amount of thecomponent (B) relative to 100 parts by weight of the component (A) ispreferably within a range from 0.5 to 30 parts by weight, morepreferably from 1 to 20 parts by weight. When the component (B) is aphotoacid generator, the amount of the component (B) is preferablywithin a range from 0.5 to 30 parts by weight, more preferably from 1 to20 parts by weight. When the amount of the component (B) is within theabove-mentioned range, formation of a resist pattern can besatisfactorily performed. When the amount of the component (B) is atleast as large as the lower limit of the above-mentioned range, thesolubility of the resist film in an alkali developing solution can bereliably increased, thereby improving the resolution. On the other hand,when the amount of the component (B) is no more than the upper limit ofthe above-mentioned range, the sensitivity becomes excellent. Further,in the case of a photoacid generator, when the amount of the component(B) is no more than the upper limit of the above-mentioned range, thetransparency of the resist film becomes excellent.

When the resist composition contains the component (B), the amount ofthe component (B) based on the total of the component (G) and thecomponent (B) is preferably 50% by weight or less, and more preferably20% by weight or less.

Other Components

In the resist composition of the present invention, a component otherthan the aforementioned components, such as an acid amplifier component,a fluorine additive, an amine or the like can be blended.

Acidic Amplifier Component (H)

In the present invention, the component (H) is decomposed by an acid togenerate a free acid, and the free acid further decomposes the component(H) to further generate free acid. In this manner, by the action ofacid, the component (H) is serially decomposed, and generates many freeacid molecules.

The component (H) is not particularly limited, as long as it isdecomposable by the action of an acid, and is capable of furthergenerating acid to self-catalytically amplify acid. Preferable examplesof the component (H) include compounds having a bridged-carbon ringskeleton structure.

Here, the term “compound having a bridged-carbon ring skeletonstructure” refers to a compound which has a structure of a bridging bondformed by a plurality of carbon rings in a molecule thereof.

By virtue of the compound having a bridged-carbon ring skeletonstructure having a bridging bond, the molecule becomes rigid, and thethermal stability of the compound is improved.

The number of carbon rings is preferably from 2 to 6, and morepreferably 2 or

The bridged carbon ring may have part or all of the hydrogen atomssubstituted with an alkyl group, an alkoxy group or the like. The alkylgroup preferably has 1 to 6 carbon atoms, more preferably 1 to 3, andspecific examples of the alkyl group include a methyl group, an ethylgroup and a propyl group. The alkoxy group preferably has 1 to 6 carbonatoms, more preferably 1 to 3, and specific examples of the alkoxy groupinclude a methoxy group and an ethoxy group. The bridged carbon ring mayhave an unsaturated bond such as a double bond.

In the present invention, it is most preferable that the bridged carbonhas, on the ring thereof, a hydroxy group and a sulfonate grouprepresented by general formula (Hs) shown below bonded to the carbonatom adjacent to the carbon atom having the hydroxy group bondedthereto. [Chemical Formula 87]

—OSO₂—R⁰  (Hs)

In the formula, R⁰ represents an aliphatic group, an aromatic group or aheterocyclic group.

In the aforementioned formula (Hs), R⁰ represents an aliphatic group, anaromatic group or a heterocyclic group.

Examples of the aliphatic group for R⁰ include a chain-like or cyclicalkyl group or an alkenyl group, and preferably has 1 to 12 carbonatoms, more preferably 1 to 10 carbon atoms.

The aromatic group may be either a monocyclic group or a polycyclicgroup, and specific examples thereof include aryl groups.

The heterocyclic group may be a monocyclic group or a polycyclic group,and specific examples thereof include groups which are derived fromvarious conventional heterocyclic compounds.

The aforementioned aliphatic group, aromatic group and heterocyclicgroup may have a substituent, and examples of the substituent include ahalogen atom, an alkyl group, an alkoxy group, an amino group, asubstituted amino group and an oxygen atom (═O).

Specific examples of the aforementioned aliphatic group and the aromaticgroup include a methyl group, an ethyl group, a propyl group, a butylgroup, an acyl group, a hexyl group, a vinyl group, a propylene group,an allyl group, a cyclohexyl group, a cyclooctyl group, abicyclohydrocarbon group, a tricyclohydrocarbon group, a phenyl group, atolyl group, a benzyl group, a phenethyl group, a naphthyl group, anaphthylmethyl group, and substitution products thereof.

Examples of the heterocyclic group include groups derived from variousheterocyclic groups, such as a 5-membered ring compound containing onehetero atom or a condensed ring compound thereof (e.g., furan,thiophene, pyrrole, benzofuran, thionaphthene, indole or carbazole); a5-membered ring compound containing two hetero atoms or a condensed ringcompound thereof (e.g., oxazole, thiazole or pyrazole); a 6-memberedring compound containing one hetero atom or a condensed ring compoundthereof (e.g., pyran, pyrone, coumarin, pyridine, quinoline,isoquinoline or acridine); and a 5-membered ring compound containing twohetero atoms or a condensed ring compound thereof (e.g., pyridazine,pyrimidine, pyrazine or phthalazine).

In the present invention, when the component (H) has, on the bridgedcarbon ring, a hydroxy group and a sulfonate group represented by theaforementioned general formula (Hs), such a component (H) is decomposedby the action of an acid to generate a new acid (R⁰SO₃H).

In this manner, one acid increases in one reaction, and the reaction isaccelerated as the reaction proceeds, thereby serially decomposing thecomponent (H).

In such a case, the strength of the generated acid in terms of the aciddissociation constant (pKa) is preferably 3 or less, and most preferably2 or less. When the pKa is 3 or less, the generated acid itself islikely to induce the self-decomposition. On the other hand, when thegenerated acid has a weaker strength, it becomes difficult to induce theself-decomposition.

Examples of the free acid (R⁰SO₃H) generated by the above reactioninclude methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid,butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid,heptanesulfonic acid, octanesulfonic acid, cyclohexanesulfonic acid,camphorsulfonic acid, trifluoromethanesulfonic acid,2,2,2-trifluoroethanesulfonic acid, benzenesulfonic acid,p-toluenesulfonic acid, p-bromobenzenesulfonic acid,p-nitrobenzenesulfonic acid, 2-thiophenesulfonic acid,1-naphthalenesulfonic acid and 2-naphthalenesulfonic acid.

Specific examples of the component (H) include compounds represented bygeneral formulae (H1) to (H4) shown below (hereafter, the compoundscorresponding to general formulae are respectively referred to as“compounds (H1) to (H4)”).

In the formulae, R⁵¹ represents a hydrogen atom, an aliphatic group oran aromatic group; and R⁵² represents an aliphatic group, an aromaticgroup or a heterocyclic group.

In the aforementioned general formulae (H1) to (H3), R⁵¹ represents ahydrogen atom, an aliphatic group or an aromatic group. The aliphaticgroup and the aromatic group for R⁵¹ is the same as defined for thealiphatic group and the aromatic group for the aforementioned R⁰. AsR⁵¹, an aliphatic group or an aromatic group is preferable, an aliphaticgroup is more preferable, a lower alkyl group is still more preferable,and a methyl group is most preferable.

In the aforementioned general formulae (H1) to (H4), R⁵² represents analiphatic group, an aromatic group or a heterocyclic group, and is thesame as defined for R⁰. As R⁵², an aliphatic group or an aromatic groupis preferable, and an aliphatic group is more preferable.

With respect to the compounds (H1) to (H4), the compound (H1) has abridge bond on the 1st and 3rd positions of the bicyclo compound, thecompounds (H2) and (H3) has a bridge bond on the 1st and 4th positionsof the bicyclo compound, and the compound (H4) has a bridge bond on the1st and 6th positions of the bicyclo compound (decarine).

Therefore, in the compounds (H1) to (H4), the conformation change of thecyclohexane ring is greatly suppressed, and hence, the ring structureexhibits rigidity.

As the component (H), for example, a compound in which the bridgedcarbon has, on the ring thereof, a hydroxy group and a sulfonate grouprepresented by general formula (Hs) bonded to the carbon atom adjacentto the carbon atom having the hydroxy group bonded thereto (such as thecompounds (H1) to (H4)) can be readily synthesized by reacting a diolcompound with a halide of the sulfonic acid. The diol compound has twoisomers, namely, cis-isomer and trans-isomer, but the cis-isomer isthermally stable, and is therefore preferably used. Further, such acompound can be stably stored as long as an acid does not coexist.

Specific examples of preferable component (H) are shown below.

Among the above examples, as the component (H), in terms of the effectsof the present invention (resolution, lithography properties), thecompound (H1) or the compound (H2) is preferable, and the compound (H1)is more preferable. More specifically, it is preferable to use at leastone member selected from the group consisting of compounds representedby chemical formulae (H1-1) to (H1-9), and it is most preferable to usea compound represented by chemical formula (H1-9).

As the component (H), one type of compound may be used, or two or moretypes of compounds may be used in combination.

When the resist composition of the present invention contains thecomponent (H), the amount of the component (H) relative to 100 parts byweight of the component (A) is preferably within a range from 0.1 to 30parts by weight, and more preferably from 1 to 20 parts by weight. Whenthe amount of the component (H) is at least as large as the lower limitof the above-mentioned range, the resolution is improved. On the otherhand, when the amount of the component (H) is no more than the upperlimit of the above-mentioned range, the sensitivity is improved.

When the component (H) and the component (G) are used in a combination,the mixing ratio of the component (H) to the component (G) in terms ofmolar ratio is preferably from 9:1 to 1:9, more preferably from 9:1 to5:5, and most preferably from 9:1 to 6:4. When the ratio of thecomponent (H) is at least as large as the lower limit of theabove-mentioned range, the resolution is improved. On the other hand,when the ratio of the component (H) is no more than the upper limit ofthe above-mentioned range, the sensitivity is improved.

Further, when the component (H) and the component (B) are used in acombination, the mixing ratio of the component (H) to the component (B)in terms of molar ratio is preferably from 9:1 to 1:9, more preferablyfrom 9:1 to 5:5, and most preferably from 9:1 to 6:4. When the ratio ofthe component (H) is at least as large as the lower limit of theabove-mentioned range, the resolution is improved. On the other hand,when the ratio of the component (H) is no more than the upper limit ofthe above-mentioned range, the sensitivity is improved.

Fluorine Additive; Component (F)

In the resist composition of the present invention, a fluorine additive(hereafter, referred to as “component (F)”) may be blended for impartingwater repellency to the resist film.

As the component (F), for example, a fluorine-containing polymericcompound described in Japanese Unexamined Patent Application, FirstPublication No. 2010-002870.

Specific examples of the component (F) include polymers having astructural unit (f1) represented by general formula (f1-1) shown below.As such polymer, a polymer (homopolymer) consisting of a structural unit(f1); a copolymer of a structural unit represented by formula (f1-1)shown below and the aforementioned structural unit (a1); and a copolymerof a structural unit represented by the formula (f1-1) shown below, astructural unit derived from acrylic acid or methacrylic acid and theaforementioned structural unit (a1) are preferable. As the structuralunit (a1) to be copolymerized with a structural unit represented byformula (f1-1) shown below, a structural unit represented by theaforementioned formula (a1-0-11) is preferable, a structural unitrepresented by the aforementioned formula (a1-1-02) is more preferable,and a structural unit represented by the aforementioned formula(a1-1-32) is most preferable.

In the formula, R is the same as defined above; R⁴⁵ and R⁴⁶ eachindependently represents a hydrogen atom, a halogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms, provided that the plurality of R⁴⁵ and R⁴⁶ may be the same ordifferent; a1 represents an integer of 1 to 5; and R⁷″ represents anorganic group containing a fluorine atom.

In formula (f1-1), R is the same as defined above. As R, a hydrogen atomor a methyl group is preferable.

In formula (f1-1), examples of the halogen atom for R⁴⁵ and R⁴⁶ includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable. Examples of the alkyl groupof 1 to 5 carbon atoms for R⁴⁵ and R⁴⁶ include the same alkyl group of 1to 5 carbon atoms for R defined above, and a methyl group or an ethylgroup is preferable. Specific examples of the halogenated alkyl group of1 to 5 carbon atoms represented by R⁴⁵ or R⁴⁶ include groups in whichpart or all of the hydrogen atoms of the aforementioned alkyl groups of1 to 5 carbon atoms have been substituted with halogen atoms. Examplesof the halogen atom include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is particularly desirable.Among these, as R⁴⁵ and R⁴⁶, a hydrogen atom, a fluorine atom or analkyl group of 1 to 5 carbon atoms is preferable, and a hydrogen atom, afluorine atom, a methyl group or an ethyl group is more preferable.

In formula (f1-1), a1 represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2.

In formula (f1-1), R⁷″ represents an organic group containing a fluorineatom, and is preferably a hydrocarbon group containing a fluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branchedor cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to15 carbon atoms, and most preferably 1 to 10 carbon atoms.

It is preferable that the hydrocarbon group having a fluorine atom has25% or more of the hydrogen atoms within the hydrocarbon groupfluorinated, more preferably 50% or more, and most preferably 60% ormore, as the hydrophobicity of the resist film during immersion exposureis enhanced.

Among these, as R⁷″, a fluorinated hydrocarbon group of 1 to 5 carbonatoms is preferable, and a methyl group, —CH₂—CF₃, —CH₂—CF₂—CF₃,—CH(CF₃)₂, —CH₂—CH₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ are mostpreferable.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (F)is preferably 1,000 to 50,000, more preferably 5,000 to 40,000, and mostpreferably 10,000 to 30,000. When the weight average molecular weight isno more than the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the weight average molecular weight is at least aslarge as the lower limit of the above-mentioned range, dry etchingresistance and the cross-sectional shape of the resist pattern becomessatisfactory.

Further, the dispersity (Mw/Mn) of the component (F) is preferably 1.0to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

As the component (F), one type may be used alone, or two or more typesmay be used in combination.

When the resist composition of the present invention contains thecomponent (F), the amount of the component (F) relative to 100 parts byweight of the component (A) is preferably within a range from 0.5 to 10parts by weight.

Amine; Component (D)

In the resist composition of the present invention, an amine (D)(hereafter, referred to as “component (D)”) may be blended.

When the resist composition contains the component (G) as an acid supplycomponent, there is a possibility that, in the resist compositionsolution, the solubility of the component (A) in an alkali developingsolution is increased by the component (G) and the like. This phenomenoncan be suppressed by controlling the component (G) to an appropriateacidity; however, the phenomenon can also be controlled by adding thecomponent (D) to decrease the acidity of the component (G) in the resistcomposition solution. It is preferable to use the component (D) becausethe freedom of choice of the material for the component (G) is improved.

In addition, by virtue of the presence of the component (D) during thestorage of the resist composition, the storage stability of the resistcomposition after preparation can be improved. Moreover, by virtue ofthe component (D) being removed from the resist film before theneutralization in step (3), the component (D) does not obstruct theneutralization between the base generated from the component (C) and theacid derived from the component (Z), thereby enabling to obtainexcellent lithography properties and excellent pattern shape.

A multitude of these components (D) have already been proposed, and anyof these known compounds may be used. Among these, as the component (D),a compound exhibiting a pKa which is the same or smaller than the pKa ofthe cation moiety of the component (G1) is preferable. That is, the pKaof the component (D) is preferably 7 or less, and more preferably 6 orless.

When the resist composition contains the component (G1), in terms ofpreventing salt exchange between the cation moiety of the component (G1)and the component (D), it is more preferable that the component (D)exhibits a pKa which is the same or smaller than the pKa of the cationmoiety of the component (G1).

When the resist composition contains the component (G2), in terms ofpreventing the acidity of the component (G2) from extremely decreasing,the basicity of the component (D) is preferably low, and the pKa of thecomponent (D) is preferably 7 or less, and more preferably 6 or less.

Examples of the component (D) which satisfies such pKa include an aminein which one “H⁺” bonded to the nitrogen atom (N) has been removed fromformula (G1c-1) described in the explanation of the component (G1).Specifically, preferable examples include the above-mentioned compoundsgiven as specific examples of formula (G1c-11) and (G1c-13) in which theterminal “NH₃ ⁺” has been replaced by “NH₂”; and compounds given asspecific examples of formula (G1c-12) in which “NH⁺” within the ring hasbeen replaced by “N”.

In addition, the component (D) is preferably an amine having arelatively low boiling point. By virtue of using an amine having arelatively low boiling point, the component (D) can be removed from theresist film during the formation of the resist film on a substrate instep (1).

As such component (D) which satisfies the above boiling point, an aminehaving a boiling point of 130° C. or lower is preferable, an aminehaving a boiling point of 100° C. or lower is more preferable, and anamine having a boiling point of 90° C. or lower is most preferable.

Specific examples of the component (D) which satisfies the above boilingpoint include aliphatic amine compounds which have a fluorinated alkylgroup, such as trifluoroethylamine(2,2,2-trifluoroethylamine),pentafluoropropylamine(2,2,3,3,3-pentafluoropropylamine),heptafluorobutylamine(1H,1H-heptafluorobutylamine),nonafluoropentylamine(1H,1H-nonafluoropentylamine),undecafluorohexylamine(1H,1H-undecafluorohexylamine),bis(2,2,2-trifluoroethyl)amine, bis(2,2,3,3,3-pentafluoropropyl)amineand 1-(2,2,2-trifluoroethyl)pyrrolidine; pyridine compounds, such aspyridine and pentafluoropyridine; and oxazole compounds, such as oxazoleand isooxyazole.

As the component (D), one type of compound may be used alone, or two ormore types may be used in combination.

When the resist composition of the present invention contains thecomponent (D), the amount of the component (D) relative to 100 parts byweight of the component (A) is preferably within a range from 0.01 to20.0 parts by weight, more preferably from 1 to 15 parts by weight, andstill more preferably from 2 to 10 parts by weight. When the amount ofthe component (D) is within the above-mentioned range, the storagestability can be improved, thereby improving the lithography propertiesand the resist pattern shape.

If desired, other miscible additives can also be added to the resistcomposition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, dyes, sensitizers and base amplifiers.

As the sensitizer, conventional sensitizers can be used, and specificexamples thereof include benzophenone-type sensitizers, such asbenzophenone and p,p′-tetramethyldiaminobenzophenone; carbazole-typesensitizers; acetophen-type sensitizers; naphthalene-type sensitizers;phenol-type sensitizers; anthracene-type sensitizers, such as9-ethoxyanthracene; biacetyl; eosin; rose bengal; pyrene; phenothiazine;and anthrone. In the resist composition, the amount of the sensitizer,relative to 100 parts by weight of the component (A) is preferably from0.5 to 20 parts by weight.

A base amplifier is decomposed by the action of a base in a chainreaction, and is capable of generating a large amount of base using asmall amount of base. Therefore, by blending a base amplifier, thesensitivity of the resist composition can be improved. As the baseamplifier, for example, those described in Japanese Unexamined PatentApplication, First Publication No. 2000-330270 and Japanese UnexaminedPatent Application, First Publication No. 2008-174515 can be used.

Organic Solvent Component; Component (S)

The resist composition used in the present invention can be prepared bydissolving the materials for the resist composition in an organicsolvent (hereafter, referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone,methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such asethylene glycol, diethylene glycol, propylene glycol and dipropyleneglycol; compounds having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; and aromatic organicsolvents such as anisole, ethylbenzylether, cresylmethylether,diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among the aforementioned examples, PGMEA, PGME, cyclohexanone and EL arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2. For example, when EL is mixed as the polar solvent, the PGMEA:ELweight ratio is preferably from 1:9 to 9:1, and more preferably from 2:8to 8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME weight ratio is preferably from 1:9 to 9:1, more preferablyfrom 2:8 to 8:2, and still more preferably 3:7 to 7:3. Alternatively,when PGME and cyclohexanone is mixed as the polar solvent, thePGMEA:(PGME+cyclohexanone) weight ratio is preferably from 1:9 to 9:1,more preferably from 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of γ-butyrolactone withPGMEA, EL or the aforementioned mixed solvent of PGMEA with a polarsolvent, is also preferable. The mixing ratio (former:latter) of such amixed solvent is preferably from 70:30 to 95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the organic solvent is used in an amount suchthat the solid content of the resist composition becomes within therange from 2 to 20% by weight, and preferably from 2 to 15% by weight.

The resist composition of the present invention described above can bepreferably used in the formation of a negative-tone resist pattern by analkali developing process.

In the method of forming the negative-tone resist pattern, a resistcomposition containing a base component that exhibits increasedsolubility in an alkali developing solution and a photobase generatorcomponent that generates a base upon exposure is coated on a substrateto form a resist film, the resist film is subjected to exposure, andbaking (post exposure bake (PEB)) is conducted. At exposed portions ofthe resist film, acid provided to the resist film in advance is reactedwith base generated from the photobase generator upon exposure to beneutralized. On the other hand, at unexposed portions of the resistfilm, by the action of the acid, the solubility of the base component inan alkali developing solution is increased. Therefore, by alkalideveloping the resist film after the PEB, the unexposed portions of theresist film are dissolved and removed, while the exposed portionsbecomes a retained film, thereby forming a negative-tone resist pattern.

In the method of forming a negative-tone resist pattern, it becomesimportant that the acid provided to the resist film in advance is notdeactivated prior to exposure, and the acid effectively acts on the basecomponent at unexposed portions by baking (PEB). Further in terms ofefficient neutralization of the acid and the base at exposed portions,it becomes important to suppress diffusion of base generated from thephotobase generator component upon exposure.

In the present invention, by virtue of the selected photobase generatorcomponent, i.e., the compound represented by general formula (C1)(component (C1)) having a specific structure, the photobase generatorcomponent prior to exposure or at unexposed portions do not act as aquencher which traps the acid provided to the resist film in advance. Onthe other hand, at exposed portions, the photobase generator componentgenerates base having a strength to sufficiently neutralize the acid, orthe photobase generator component generates base having a strength tosuppress the deprotection reaction of the component (A) by the action ofthe acid, thereby giving a contrast between the unexposed portions andthe exposed portions. As a result, a negative-tone resist compositioncan be formed with a high resolution.

In addition, by virtue of the amine generated from the component (C1)having a bulky “nitrogen-containing, 6-membered ring structure”, theamine is suppressed from being diffused to unexposed portions of theresist film (the diffusion length of the base can be shortened), therebyreducing the amount of unexposed portions remaining undissolved.Furthermore, by virtue of the component (C1) having an oxygen atom (theoxygen atom of —OR³), the component (C1) exhibits a relatively highpolarity, and is more likely to interact with the base component (A). Asa result, the component (C1) can be uniformly distributed within theresist film.

Moreover, by virtue of the component (C1) having a photofunctional group“(aromatic group formed by R¹ and the two carbon atoms bonded to R¹ andsubstituted with a nitro group)-C(R²)—O—”, the base generationefficiency (reaction efficiency of the photofunctional portion) isenhanced, and the photoadsorption property can be controlled.

Thus, by using a resist composition including a photobase generatorcomponent containing the component (C1), a resist pattern with anexcellent dimension uniformity and no fluctuation in the dimension canbe formed. Further, by such method of forming a negative-tone resistpattern, a negative-tone resist pattern can be formed with a highresolution and an excellent shape.

Furthermore, the resist composition of the present invention ispreferably used in step (1) of the method of forming a resist patternincluding steps (1) to (4) described below.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to the presentinvention includes: a step (1) in which a resist composition including abase component (A) that exhibits increased solubility in an alkalideveloping solution and a photo-base generator component (C) thatgenerates a base upon exposure and contains a compound represented bygeneral formula (C1) shown below is applied to a substrate to form aresist film; a step (2) in which the resist film is subjected toexposure; a step (3) in which baking is conducted after the step (2),such that, at an exposed portion of the resist film, the base generatedfrom the photobase generator component (C) upon the exposure and an acidprovided to the resist film in advance are neutralized, and at anunexposed portion of the resist film, the solubility of the basecomponent (A) in an alkali developing solution is increased by theaction of the acid provided to the resist film in advance; and a step(4) in which the resist film is subjected to an alkali development,thereby forming a negative-tone resist pattern in which the unexposedportion of the resist film has been dissolved and removed.

In formula (C1), R¹ represents a group which forms an aromatic ringtogether with the two carbon atoms bonded to the R¹ group, provided thatthe aromatic ring may have a nitro group or a substituent other than thenitro group bonded to the aromatic ring; R² represents a hydrogen atomor a hydrocarbon group which may have a substituent; and R³ represents ahydrogen atom, a carboxy group or a hydrocarbon group of 1 to 15 carbonatoms which may have a substituent, provided that part of the carbonatoms constituting the hydrocarbon group for R³ may be replaced with ahetero atom.

In the method of forming a resist pattern according to the presentinvention, the resist composition used in step (1) is the same asdefined for the aforementioned resist composition of the presentinvention. The compound represented by general formula (C1) is the sameas defined for the aforementioned component (C1).

Hereinbelow, the method of forming a resist pattern according to thepresent invention will be described, with reference to the drawings.However, the present invention is not limited to these embodiments.

FIRST EMBODIMENT

FIG. 1 shows an example of one embodiment of the method of forming aresist pattern according to the present invention.

In this embodiment, a resist composition containing a base componentthat exhibits increased solubility in an alkali developing solution(component (A)), a photobase generator component (component (C))containing a compound represented by the aforementioned general formula(C1) (component (C1)), and an acidic compound component (component (G))as an acid supply component (component (Z)) is used.

Firstly, as shown in FIG. 1A, the resist composition is applied to asubstrate 1 to form a resist film 2 (step (1); FIG. 1A).

Next, as shown in FIG. 1( b), the thus formed resist film 2 is subjectedto exposure through a photomask 3 having a predetermined pattern formedthereon. As a result, in the exposed region (exposed portions) of theresist film 2, a base is generated from the component (C1) upon exposure(step (2); FIG. 1( b)).

After exposure, baking (post exposure bake (PEB)) is conducted. By thisbaking, at the unexposed portions 2 b of the resist film 2, thesolubility of the component (A) in an alkali developing solution can beincreased by the action of the acid (component (G)) provided to theresist film 2 by adding the component (G) to the resist composition. Onthe other hand, at exposed portions 2 a, a neutralization reactionbetween the base generated from the component (C1) upon exposure and theacid supplied to the resist film (component (G)) proceeds, so that thesolubility of the component (A) in an alkali developing is eitherunchanged or only slightly changed. As a result, a difference in thedissolution rate in an alkali developing solution (dissolution contrast)occurs between the exposed portions 2 a and the unexposed portions 2 b(step (3); FIG. 1( c)).

Thereafter, developing is conducted using an alkali developing solution.By conducting development, the exposed portions 2 a of the resist film 2a remains, and the unexposed portions 2 b of the resist film 2 aredissolved and removed. As a result, as shown in FIG. 1D, a resistpattern including a plurality of resist patterns arranged at intervalsis formed on the substrate 1.

[Step (1)]

In this embodiment, a resist composition including component (A),component (C) containing component (C1) and component (G) as component(Z) is applied to a substrate 1, thereby forming a resist film 2.

The substrate 1 is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate 1, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used, and a substrate provided with an organic film ispreferable. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.It is particularly desirable that an organic film is provided because apattern can be reliably formed on the substrate with a high aspect ratiowhich is useful in the production of semiconductors.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer film) and at least one layer of a resistfilm are provided on a substrate, and a resist pattern formed on theupper resist film is used as a mask to conduct patterning of thelower-layer film. This method is considered as being capable of forminga pattern with a high aspect ratio. The multilayer resist method isbroadly classified into a method in which a double-layer structureconsisting of an upper-layer resist film and a lower-layer film isformed, and a method in which a multilayer structure having at leastthree layers composed of an upper-layer resist film, a lower-layer filmand at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer film.In the multilayer resist method, a desired thickness can be ensured bythe lower-layer film, and as a result, the thickness of the resist filmcan be reduced, and an extremely fine pattern with a high aspect ratiocan be formed.

An inorganic film can be formed, for example, by coating an in organicanti-reflection film composition such as a silicon-based material on asubstrate, followed by baking.

An organic film can be formed, for example, by dissolving a resincomponent and the like for forming the film in an organic solvent toobtain an organic film-forming material, coating the organicfilm-forming material on a substrate using a spinner or the like, andbaking under heating conditions preferably in the range of 200 to 300°C. for 30 to 300 seconds, more preferably for 60 to 180 seconds. Theorganic film-forming material does not need to have susceptibility tolight or electron beam like a resist film, and the organic film-formingmaterial may or may not have such susceptibility. More specifically, aresist or a resin generally used in the production of a semiconductordevice or a liquid crystal display device can be used.

Further, it is preferable that the organic film-forming material can besubjected to etching, particularly dry etching, so that, by etching theorganic film using a resist pattern, the resist pattern can betransferred to the organic film, and an organic film pattern can beformed. It is particularly desirable to use an organic film-formingmaterial which can be subjected to oxygen plasma etching or the like. Assuch an organic film-forming material, a material conventionally usedfor forming an organic film such as an organic BARC can be used.Examples of such an organic film-forming material include the ARC seriesmanufactured by Brewer Science Ltd., the AR series manufactured by Rohmand Haas Company, and the SWK series manufactured by Tokyo Ohka KogyoCo., Ltd.

In this embodiment, the component (G) contained in the resistcomposition neutralizes the base generated from the component (C1) uponexposure in steps (2) and (3) described later; and in step (3) describedlater, the component (G) acts on the component (A) as an acid uponbaking (PEB), thereby increasing the solubility of the component (A) inan alkali developing solution.

In addition, by virtue of the component (C) containing the component(C1), the acid (component (G)) is unlikely to be deactivated by theinfluence of the component (C) prior to exposure. Thus, by the baking instep (3), the acid (component (G)) present at unexposed portionseffectively act on the component (A).

The explanation of the resist composition is the same as the explanationof the resist composition of the present invention.

The method of applying the resist composition to the substrate 1 to forma resist film 2 is not particularly limited, and the resist film 2 canbe formed by a conventional method.

For example, the resist composition can be applied to the substrate 1 bya conventional method such as a spin-coating method using a spinner, abar-coating method using a bar coater, or the like, followed by dryingat room temperature on a cooling plate or the like, or prebaking (PAB),thereby forming a resist film 2.

In the present invention, “prebake” refers to a heat treatment of 70° C.or higher that is conducted after applying the resist composition to thesubstrate and before conducting exposure using a hot plate or the like.

When a prebaking treatment is conducted, the temperature conditions ispreferably from 80 to 150° C., and more preferably from 80 to 100° C.The prebaking time is preferably from 40 to 120 seconds, and morepreferably from 60 to 90 seconds.

By conducting prebaking, the organic solvent can be volatilized evenwhen the resist film has a large film thickness.

By drying the resist composition at room temperature and not conductingprebaking, the number of steps in the formation of a resist pattern canbe reduced, and the resolution of the resist pattern can be enhanced.

Whether or not a prebaking is conducted can be suitably determineddepending on the advantages in view of the materials used for the resistcomposition, and target of the pattern to be formed.

The film thickness of the resist film 2 formed in step (1) is preferablywithin the range from 50 to 500 nm, and more preferably from 50 to 450nm. By ensuring that the thickness of the resist film satisfies theabove-mentioned range, a resist pattern with a high level of resolutioncan be formed, and a satisfactory level of etching resistance can beachieved.

Further, in the case where a prebaking is not conducted, the filmthickness of the resist film 2 formed in step (1) is preferably 300 nmor less, more preferably 200 nm or less, and most preferably from 50 to150 nm. When the film thickness of the resist film 2 is no more than theupper limit of the preferable range, by a coating method such as aspin-coating method at room temperature without prebaking, the organicsolvent is less likely to remain in the resist film, and the resist filmcan be more reliably dried, thereby improving the uniformity of the filmthickness of the resist film 2 (i.e., the in-plane uniformity of thesubstrate 1). The effects of not conducting a prebaking become moresignificant as the film thickness of the resist film becomes smaller.

[Step (2)]

In the present embodiment, the resist film 2 formed in the step (1) isselectively exposed through a photomask 3. As a result, at exposedportions 2 a, a base is generated from the component (C1) upon exposure,and a neutralization reaction between the base and the acid (component(G)) within the resist film 2 is started.

With respect to the exposure dose, an amount capable of generating abase from the component (C1) in an amount necessary to neutralize theacid (component (G)) present in the exposed portions 2 a is sufficient.

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as KrF excimer laser,ArF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. In terms of forming a fine resist pattern, ArF excimer laser,EUV or EB is preferable, and ArF excimer laser is particularlydesirable.

The photomask 3 is not particularly limited, and a conventional mask canbe used. For example, a binary mask in which the transmittance of thelight shielding portion is 0% or a halftone-phase shift mask (HT-mask)in which the transmittance of the light shielding portion is 6% can beused. The unexposed portions can be selectively formed by using ahalftone-phase shift mask.

As a binary mask, those in which a chromium film, a chromium oxide film,or the like is formed as a light shielding portion on a quartz glasssubstrate are generally used.

A phase shift mask is a photomask provided with a portion (shifter)which changes the phase of light. Thus, by using a phase shift mask,incidence of light to unexposed portions can be suppressed, and thedissolution contrast to an alkali developing solution can be improvedbetween unexposed portions and exposed portions. As a phase shift maskother than a halftone-phase shift mask, a Levenson-phase shift mask canbe mentioned. As any of these phase shift masks, commercially availablemasks can be used.

Specific examples of the half-tone type phase shift masks include thosein which an MoSi (molybdenum silicide) film, a chromium film, a chromiumoxide film, an silicon oxynitride film, or the like is formed as a lightshielding portion (shifter) exhibiting a transmittance of about several10% (generally 6%) on a substrate generally made of quartz glass.

In the present embodiment, exposure is conducted through a photomask 3,but the present invention is not limited to this embodiment. Forexample, the exposure may be conducted without using a mask, e.g.,selective exposure by drawing with electron beam (EB) or the like.

The exposure of the resist film 2 can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography) through an immersion medium.In step (2), in terms of forming a resist pattern with a highresolution, it is preferable to conduct exposure through an immersionmedium.

In immersion lithography, exposure (immersion exposure) is conducted ina state where the region between the lens and the resist film 2 formedon the substrate 1 (which was conventionally filled with air or an inertgas such as nitrogen) is filled with a solvent (a immersion medium) thathas a larger refractive index than the refractive index of air.

More specifically, in immersion lithography, the region between theresist film 2 formed in the above-described manner and lens at thelowermost portion of the exposure apparatus is filled with a solvent (animmersion medium) that has a larger refractive index than the refractiveindex of air, and in this state, the resist film 2 is subjected toexposure (immersion exposure) through a predetermined photomask 3.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film 2 to be subjected to immersion exposure. The refractiveindex of the immersion medium is not particularly limited as long at itsatisfies the above-mentioned requirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film 2 include water, fluorine-basedinert liquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the immersion medium afterthe exposure can be removed by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

[Step (3)]

In the present embodiment, after the step (2), baking (post exposurebake (PEB)) is conducted.

In the baking, the temperature conditions is preferably from 50 to 200°C., more preferably from 80 to 150° C., and still more preferably from90 to 130° C. The baking time is preferably from 10 to 300 seconds, morepreferably from 40 to 120 seconds, and still more preferably from 60 to90 seconds.

In this manner, by conducting baking of the resist film 2 afterexposure, in the entire resist film 2, the component (G) blended withinthe resist composition acts as acid, and at unexposed portions 2 b, bythe action of the acid (component (G)), the solubility of the component(A) in an alkali developing solution is increased. On the other hand, atexposed portions 2 a, a neutralization reaction between the basegenerated from the component (C1) upon exposure and the acid (component(G)) proceeds, so that the amount of acid which would act on thecomponent (A) decreases. As a result, the solubility of the component(A) in an alkali developing is either unchanged or only slightlychanged. As such, a difference in the dissolution rate in an alkalideveloping solution (dissolution contrast) occurs between the exposedportions 2 a and the unexposed portions 2 b.

The baking in this step (3) does not necessarily control the start ofthe neutralization reaction.

[Step (4)]

In the present embodiment, after the step (3), by conducting alkalideveloping, the unexposed portions 2 b of the resist film 2 aredissolved and removed, and the exposed portions 2 a are retained,thereby forming a negative resist pattern.

Specific examples of the alkali developing solution include inorganicalkalis, such as sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium silicate, sodium metasilicate and aqueous ammonia;primary amines, such as ethylamine and n-propyl amine; secondary amines,such as diethylamine and di-n-butylamine; tertiary amines, such astriethylamine and methyldiethylamine; alcoholamines, such asdimethylethanolamine and triethanolamine; quaternary ammonium salts,such as tetramethylammonium hydroxide and tetraethylammonium hydroxide;and cyclic amines, such as pyrrole and piperidine.

Among these examples, as the alkali developing solution, an aqueousalkali solution containing at least one member selected from the groupconsisting of primary amines, secondary amines, tertiary amines andquaternary ammonium salts is preferable, and an aqueous solution oftetramethylammonium hydroxide (TMAH) is particularly desirable.

Further, the aforementioned aqueous alkali solution having alcohols,surfactants added thereto in an appropriate amount may be used.

In general, the alkali concentration within the alkali developingsolution (i.e., concentration of inorganic alkalis, quaternary ammoniumsalts or amine compounds, based on the total weight of the alkalideveloping solution) is from 0.01 to 20% by weight.

The alkali developing treatment can be performed by a conventionalmethod.

After the alkali development, a rinse treatment using pure water or thelike may be conducted.

In addition, after the alkali development, a further baking (post bake)may be conducted. Post bake (which is performed in order to remove watercontent after the alkali developing and rinsing) is generally conductedat about 100° C. preferably for 30 to 90 seconds.

In the first embodiment described above, a resist composition containinga component (G) as the component (Z) is used. However, a resistcomposition containing an acid generator component (B) (a thermal acidgenerator, a photoacid generator or the like) instead of the component(G) or together with the component (G) may be used. Further, an acidamplifier component (H) may be used in combination with at least one ofthe component (G) and the component (B), since the acid concentrationcan be enhanced by a bake treatment such as PEB.

As the component (B), either or both of a compound which generates acidupon heating (thermal acid generator) and a compound which generatesacid upon exposure (photoacid generator) can be used.

In the case where a resist composition containing a thermal acidgenerator as the component (B) is used, by the baking (PEB) in the step(3), in the entire resist film 2, acid is generated from the thermalacid generator. At the unexposed portions 2 b of the resist film 2, bythe action of the acid generated from the thermal acid generator by thebaking (PEB), the solubility of the component (A) in an alkalideveloping solution is increased. On the other hand, at exposed portions2 a of the resist film 2, a neutralization reaction between the acidgenerated from the thermal acid generator by the baking (PEB) and thebase generated from the component (C1) upon exposure in the step (2)proceeds, so that the solubility of the base component (A) in an alkalideveloping is either unchanged or only slightly changed. As such, adifference in the dissolution rate in an alkali developing solution(dissolution contrast) occurs between the exposed portions 2 a and theunexposed portions 2 b.

In the case where a resist composition containing a thermal acidgenerator is used, it is preferable not to conduct the aforementionedprebaking. By virtue of not conducting the prebaking, acid derived fromthe thermal acid generator does not act on the component (A) afterapplying the resist composition on the substrate and until exposure. Asa result, the contrast between the exposed portions 2 a and theunexposed portions 2 b of the resist film 2 is improved, such that anegative-tone resist pattern can be reliably formed with a highresolution.

Further, by appropriately selecting the photomask, the component (A),the component (C) and the like, a photoacid generator can be used as thecomponent (B). For example, an embodiment in which a resist compositioncontaining a photoacid generator having a relatively long diffusionlength and a component (C1) having a relatively short diffusion lengthis used, and a photomask having transparency (a halftone-phase shiftmask) can be mentioned. With respect to the diffusion length of acid orbase, the diffusion length of acid can be controlled by skeleton orpolarity of the anion moiety of the photoacid generator, and thediffusion length of base can be controlled by molecular weight andskeleton of the base after photodecomposition of the component (C1).

In such an embodiment, by exposure in the step (2), at exposed portions2 a, base is generated from the component (C), and acid is generatedfrom the photoacid generator. At unexposed portions 2 b, by the bakingin the step (3), acid generated at exposed portions 2 a and diffused tounexposed portions 2 b acts on the component (A) to cause dissociationof the protection groups (deprotection reaction proceeds), therebyincreasing the solubility of the component (A) in an alkali developingsolution. On the other hand, at exposed portions 2 a, neutralizationreaction between the base and acid generated in the step (2) proceeds,so that the solubility of the component (A) in an alkali developing iseither unchanged or only slightly changed. As such, a difference in thedissolution rate in an alkali developing solution (dissolution contrast)occurs between the exposed portions 2 a and the unexposed portions 2 b.

SECOND EMBODIMENT

FIG. 2 shows an example of another embodiment of the method of forming aresist pattern according to the present invention. In this embodiment, aresist composition containing a base component that exhibits increasedsolubility in an alkali developing solution (component (A)) and aphotobase generator component (component (C)) containing a component(C1), and an organic film forming composition containing a component (G)is used.

Firstly, as shown in FIG. 2( a), the resist composition is applied to asubstrate 1 to form a resist film 2′ (step (1); FIG. 2( a)).

Next, as shown in FIG. 2( b), the resist film 2′ is subjected toexposure through a photomask 3 having a predetermined pattern formedthereon. As a result, in the exposed region (exposed portions) of theresist film 2′, a base is generated from the component (C1) uponexposure (step (2); FIG. 2( b)).

Following exposure, the organic film-forming composition is coated onthe first resist film 2′ (step (5); FIG. 2( c)).

Thereafter, baking (PEB) is conducted. As a result, an organic film 4 isformed, and the component (G) contained in the organic film 4 isdiffused to the resist film 2′, thereby providing acid to the resistfilm 2′. At the exposed portions 2′c of the resist film 2′, theneutralization reaction between the base generated from the component(C1) upon the exposure and the acid provided from the organic film 4proceeds. Thus, the solubility of the component (A) in an alkalideveloping is either unchanged or only slightly changed. On the otherhand, at unexposed portions 2 d′, the solubility of the component (A) inan alkali developing solution is increased by the action of the acidprovided from the organic film 4. As a result, a difference in thedissolution rate in an alkali developing solution (dissolution contrast)occurs between the exposed portions 2′c and the unexposed portions 2′d(step (3); FIG. 2( d)).

Thereafter, developing is conducted using an alkali developing solution.By conducting development, the exposed portions 2 c′ of the resist film2′ remain, and the unexposed portions 2′d of the resist film 2′ aredissolved and removed. As a result, as shown in FIG. 2( e), a resistpattern including a plurality of resist patterns 2′c arranged atintervals is formed on the substrate 1 (step (4); FIG. 2( e)).

[Step (1), Step (2)]

In this embodiment, the step (1) and the step (2) can be performed inthe same manner as in the step (1) and the step (2) in theaforementioned first embodiment, respectively. However, the resistcomposition used in this embodiment may or may not contain a component(Z).

[Step (5)]

In this embodiment, after the step (2), an organic film-formingcomposition containing the component (G) is coated on the resist film 2′by a conventional method, e.g., a method using a spinner or the like. Inthis manner, the organic film-forming composition is coated on theresist film 2′ and the resist film 2′ is allowed to come into contactwith an acid in a step prior to the step (3) described below, therebyenabling to provide the acid to the resist film 2′ by the baking in thestep (3).

The coating conditions of the organic film-forming composition can beappropriately selected depending on the desired thickness (filmthickness) of the organic film 4 to be formed.

The thickness of the organic film 4 can be appropriately selecteddepending on the type of component (G) blended in the organicfilm-forming composition or the process conditions such as immersionexposure, but is preferably from 10 to 300 nm, more preferably from 20to 200 nm, and still more preferably from 30 to 150 nm. When thethickness of the organic film 4 is within the above-mentioned range, asatisfactory amount of acid can be provided to the resist film 2′, and aresist pattern can be reliably formed with a high resolution.

Specific examples of the organic film-forming composition will bedescribed later.

[Step (3)]

In the present embodiment, after the step (5), baking (post exposurebake (PEB)) is conducted.

In this embodiment, the step (3) can be performed in the same manner asin the step (3) in the aforementioned first embodiment.

By conducting PEB, an organic film 4 is formed on the resist film 2′,and the component (G) contained in the organic film 4 is diffused fromthe organic film 4 to the resist film 2′, thereby providing acid to theresist film 2′. In the resist film 2′, at unexposed portions 2 d′, thesolubility of the component (A) in an alkali developing solution isincreased by the action of the acid provided from the organic film 4. Onthe other hand, at exposed portions 2 a, a neutralization reactionbetween the base generated from the component (C1) upon exposure and theacid provided from the organic film 4 proceeds, so that the amount ofacid which would act on the component (A) decreases. Therefore, thesolubility of the component (A) in an alkali developing is eitherunchanged or only slightly changed.

As a result, a difference in the dissolution rate in an alkalideveloping solution (dissolution contrast) occurs between the exposedportions 2′c and the unexposed portions 2′d.

In the case where the organic film-forming composition contains aphotoacid generator component in addition to the component (G) as thecomponent (Z), and step (5) is conducted before step (2), acid isgenerated from the photoacid generator upon exposure in step (2). Likethe component (G), the generated acid is supplied to the resist film 2′in step (3). At exposed portions 2 a of the resist film 2′, the acid isneutralized by a base generated from the component (C1) upon exposure,or is diffused from the exposed portions 2′c to the unexposed portions2′d to act on the component (A), thereby increasing the solubility ofthe component (A) in an alkali developing solution.

In the case where the resist composition contains a thermal acidgenerator component in addition to the component (G) as the component(Z), acid is generated from the thermal acid generator component by thePEB in this step. Like the component (G), the generated acid is suppliedto the resist film 2′ in step (3). At exposed portions 2 a of the resistfilm 2′, the acid is neutralized by a base generated from the component(C1) upon exposure, or is diffused from the exposed portions 2′c to theunexposed portions 2′d to act on the component (A), thereby increasingthe solubility of the component (A) in an alkali developing solution.

By generation of such dissolution contrast, a high-resolutionnegative-tone resist pattern can be obtained by alkali developing instep (4).

The baking in this step (3) does not necessarily control the start ofthe neutralization reaction.

[Step (4)]

In the present embodiment, after the step (3), by conducting alkalideveloping, the unexposed portions 2′d of the resist film 2′ aredissolved and removed, and the exposed portions 2′c are retained,thereby forming a negative resist pattern.

As the alkali developing solution, the same as those described above canbe used.

The alkali developing can be conducted by a conventional method,preferably using an aqueous tetramethylammonium hydroxide (TMAH)solution having a concentration of 0.1 to 10% by weight.

After the alkali development, a rinse treatment using pure water or thelike may be conducted.

In addition, after the alkali development, a further baking (post bake)may be conducted. Post bake (which is performed in order to remove watercontent after the alkali developing and rinsing) is generally conductedat about 100° C. preferably for 30 to 90 seconds.

With respect to the organic film 4 formed on the resist film 2′, it ispreferable to select the material for forming the organic film 4 (e.g.,an alkali-soluble resin), so as to dissolve and remove the organic film4 in the alkali developing treatment in the step (4). Alternatively, theresist film 4 can be removed by a conventional method between the step(3) and the step (4).

In the second embodiment described above, an organic film-formingcomposition containing the component (G) is used. However, an organicfilm-forming composition containing an acid generator component (B) (aphotoacid generator, a thermal acid generator) instead of the component(G) or together with the component (G) may be used. With respect to thethermal acid generator and the photoacid generator, either one may beused, or both may be used in combination. However, in the case where aphotoacid generator component is used as the component (B), step (5) isconducted between step (1) and step (2).

In this manner, upon exposure in step (2), acid is generated from thephotoacid generator component, and the acid is supplied to the resistfilm 2′ by baking in step (3).

Further, as the method of forming a resist pattern according to thepresent invention, an embodiment other than the first and secondembodiments may be used. For example, between steps (2) and (3) in thefirst embodiment, a step (5) may be conducted in which an organicfilm-forming composition containing a component (Z) coated on the resistfilm to form an organic film. After exposure, by coating the organicfilm-forming composition on the resist film, followed by baking (PEB),an organic film is formed on the resist film, and acid derived from thecomponent (Z) contained in the organic film is diffused from the organicfilm to the resist film, thereby supplying acid to the resist film.Thereafter, by conducting developing by an alkali developing solution, anegative-tone resist pattern with a high contrast can be formed. In thecase where a photoacid generator is used as the component (Z), the step(5) can be conducted between steps (1) and (2).

Alternatively, instead of using an organic film-forming composition, anembodiment in which an acidic, activated rinse is applied to the resistfilm can be used. As the acidic, activated rinse, an aqueous solutioncontaining a component (G2) described above can be used.

In the method of forming a resist pattern according to the presentinvention, after forming a negative resist pattern in the manner asdescribed above, etching of the substrate 1 may be conducted using thenegative resist pattern as a mask. By conducting such etching totransfer the resist pattern to the substrate 1, a semiconductor deviceor the like can be produced.

The etching can be conducted by a conventional method. For example, whenthe substrate 1 has an organic film formed thereon, the etching of theorganic film is preferably conducted by dry etching. Among dry etching,especially in terms of production efficiency, oxygen-plasma etching oretching using a CF₄ gas or a CHF₃ gas is preferable, and oxygen-plasmaetching is more preferable.

Etching of the substrate is preferably performed using a halogen gas,more preferably using a fluorinated carbon-based gas, and mostpreferably using a CF₄ gas or a CHF₃ gas.

(Organic Film-Forming Composition)

In the method of forming a resist pattern according to the presentinvention, as shown in the aforementioned second embodiment, forsupplying acid to the resist film, an organic film forming compositioncontaining an acid supply component (Z) (component (G), component (B))may be used.

The organic film-forming composition may contain, for example, a resin,an organic solvent and the like, in addition to the component (Z).

As the acid supply component (Z) for the organic film formingcomposition, the same acid supply components as those described abovefor the component (Z) in the explanation of the aforementioned resistcomposition can be given.

As the acid supply component (Z), one type of compound may be used, ortwo or more types of compounds may be used in combination.

In the case where the organic film forming composition contains acomponent (Z), a resin and an organic solvent, the amount of thecomponent (Z) relative to 100 parts by weight of the resin is preferably0.1 to 60 parts by weight. When the component (Z) is a component (G),the amount of the component (Z) relative to 100 parts by weight of theresin is preferably 0.1 to 50 parts by weight, and more preferably 1 to20 parts by weight. When the component (Z) is a component (B), theamount of the component (Z) relative to 100 parts by weight of the resinis preferably 1 to 60 parts by weight, and more preferably 1 to 50 partsby weight.

When the amount of the component (Z) is at least as large as the lowerlimit of the above-mentioned range, a satisfactory amount of acid issupplied to the resist film, and the solubility of the unexposedportions in an alkali developing solution can be reliably increased,thereby improving the resolution. On the other hand, when the amount ofthe component (Z) is no more than the upper limit of the above-mentionedrange, the sensitivity is improved. Further, by virtue of theabove-mentioned range, when each of the components are dissolved in anorganic solvent, a uniform solution can be obtained and the storagestability becomes satisfactory.

[Resin]

The resin is not particularly limited as long as it is capable offorming an organic film, and any conventional resin can be used.

Among the conventional resins, it is preferable to use an alkali-solubleresin because in step (4), the formed organic film can be removed duringthe formation of a resist pattern by alkali developing.

As the alkali-soluble resin, any resin having an alkali-soluble groupmay be used, and examples thereof include conventional resins such asnovolak resins, hydroxystyrene resins, acrylic resins andpolycycloolefin resins.

Specific examples of the alkali-soluble group include a phenolic hydroxygroup, a carboxy group, a fluorinated alcohol group, a sulfonate group,a sulfonamide group, a sulfonylimide group, an(alkylsulfonyl)(alkylcarbonyl)methylene group, an(alkylsulfonyl)(alkylcarbonyl)imide group, a bis(alkylcarbonyl)methylenegroup, a bis(alkylcarbonyl)imide group, a bis(alkylsulfonyl)methylenegroup, a bis(alkylsulfonyl)imide group, a tris(alkylcarbonyl)methylenegroup, a tris(alkylsulfonyl)methylene group, and a group containing anyof these groups.

As an example of an alkali-soluble resin, a polymer (A″) having astructural unit derived from a polycycloolefin (hereafter, thisstructural unit is referred to as “structural unit (a′1)”) can bepreferably used.

As the structural unit (a′1), a structural unit having a basic skeletonrepresented by general formula (a′1-0) shown below is preferable.

In the formula, a″ represents 0 or 1.

In formula (a′1-0), a″ represents 0 or 1. In terms of industrialavailability, a″ is preferably 0.

In the present description, a “structural unit having a basic skeletonrepresented by general formula (a′1-0)” may be either a structural unitrepresented by general formula (a′1-0) per se (i.e., a structural unitderived from bicyclo[2.2.1]-2-heptene(norbornene) or a structural unitderived from tetracyclo[4.4.0.1^(2,5).1^(7,10)]-3-dodecene), or astructural unit having a substituent on the ring skeleton. In otherwords, a “structural unit having a basic structure represented bygeneral formula (a′1-0)” includes structural units in which part or allof the hydrogen atoms bonded to the carbon atoms that constitute thecyclic structure (namely, bicyclo[2.2.1]-2-heptane ortetracyclo[4.4.0.1^(2,5).1^(7,10)]-3-dodecane) are substituted with anatom or a substituent other than hydrogen.

As the structural unit (a′1), in particular, a structural unitrepresented by general formula (a′1-1) shown below can be given as anexample.

In formula (a′1-1), a″ is the same as defined for a″ in theaforementioned formula (a′1-0).

c″ represents an integer of 1 to 5, preferably an integer of 1 to 3, andmost preferably 1.

b represents an integer of 1 to 5, preferably an integer of 1 to 3, andmost preferably 1.

As the structural unit (a′1), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In the polymer (A″), the amount of the structural unit (a′1) based onthe combined total of all structural units constituting the polymer (A″)is preferably 1 mol % or more, more preferably from 1 to 50 mol %, stillmore preferably 1 to 45 mol %, and still more preferably 5 to 35 mol %.When the amount of the structural unit (a′1) is within theabove-mentioned range, a predetermined alkali solubility can be reliablyachieved.

A monomer for deriving a structural unit (a′1) can be synthesized, forexample, by a method disclosed in U.S. Pat. No. 6,420,503.

Further, the polymer (A″) may include, in addition to the structuralunit (a′1), a structural unit derived from a polycycloolefin which has afluorinated alkyl group as a substituent (hereafter, this structuralunit is referred to as “structural unit (a′2)”), specifically, astructural unit represented by general formula (a′2-1) shown below.

In the formula, R²⁷ represents a fluorinated alkyl group; and a″represents 0 or 1.

In formula (a′2-1), a″ represents 0 or 1. In terms of industrialavailability, a″ is preferably 0.

In the aforementioned formula (a′2-1), R²⁷ represents a fluorinatedalkyl group, i.e., a linear, branched or cyclic alkyl group in whichpart or all of the hydrogen atoms have been substituted with a fluorineatom.

The linear or branched alkyl group is preferably an alkyl group of 1 to10 carbon atoms, more preferably an alkyl group of 1 to 8 carbon atoms,and still more preferably an alkyl group of 1 to 5 carbon atoms.Examples of alkyl groups include a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, apentyl group, an isopentyl group and a neopentyl group. Among these, apropyl group is particularly desirable.

The cyclic alkyl group preferably has 4 to 12 carbon atoms, morepreferably 5 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

Among the above examples, the fluorinated alkyl group for R²⁷ ispreferably a linear or branched alkyl group in which one hydrogen atomhas been substituted with a perfluoroalkyl group (a group in which analkylene group is bonded to a perfluoroalkyl group), more preferably—(CH₂)_(f′)—CF₃ or —(CH₂)_(f′)—C₂F₅ [f″=1 to 3], and most preferably—CH₂—CF₃ or —CH₂—C₂F₅.

As the fluorinated alkyl group, in particular, a fluorinated alkyl grouphaving a fluorination ratio (the percentage of the number of fluorineatoms based on the total number of hydrogen atoms and fluorine atomswithin the fluorinated alkyl group) of 30 to 90% is preferable, and afluorinated alkyl group having a fluorination ratio of 50 to 80% is morepreferable. When the fluorination ratio is 30% or more, the effect ofimproving the hydrophobicity of the organic film surface under immersionexposure conditions becomes excellent. Further, when the fluorinationratio is 90% or less, the development properties are improved.

In the structural unit represented by the aforementioned formula(a′2-1), the ring structure constituting the main chain may have asubstituent on the ring. Examples of the substituent include an alkylgroup of 1 to 5 carbon atoms, a fluorine atom and a fluorinated alkylgroup.

When the structural unit (a′2) is included in the polymer (A″), theamount of the structural unit (a′2), based on the combined total of allthe structural units that constitute the polymer (A″), is preferablyfrom 5 to 75 mol %, more preferably from 10 to 70 mol %, and still morepreferably from 15 to 60 mol %. When the amount of the structural unit(a′2) is within the above-mentioned range, the hydrophobicity of theorganic film surface is enhanced, and the controllability of thedissolution rate in an alkali developing solution becomes excellent.

A monomer for deriving a structural unit represented by theaforementioned formula (a′2-1) can be synthesized, for example, by amethod disclosed in Japanese Unexamined Patent Application, FirstPublication No. 2000-235263 [a method in which a fluorinated alkyl esterof (meth)acrylic acid is reacted with cyclopentadiene ordicyclopentadiene by a conventional Diels-Alder reaction].

As the polymer (A″), one type of polymer may be used alone, or two ormore polymers may be used in combination.

In the present invention, as the polymer (A″), a polymer that includes acombination of structural units such as that shown below is particularlydesirable.

In the formula, b and c″ are the same as defined above; and R²⁷′represents a fluorinated alkyl group of 1 to 5 carbon atoms.

c″ is preferably an integer of 1 to 3, and most preferably 1.

b is preferably an integer of 1 to 3, and most preferably 1.

It is most preferable that R²⁷′ represents —CH₂—CF₃ or —CH₂—C₂F₅.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the polymer (A″)is not particularly limited, but is preferably 1,000 to 50,000, morepreferably 1,500 to 30,000, and most preferably 2,000 to 20,000. Whenthe polymer (A′) has a weight average molecular weight within theabove-mentioned range, the polymer (A′) exhibits a satisfactorysolubility in an organic solvent when used as a resin component forforming an organic film. Further, the alkali development properties andthe film formability becomes excellent.

Further, the dispersity (Mw/Mn) of the polymer (A″) is not particularlylimited, but is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, andmost preferably 1.0 to 2.5.

The polymer (A″) can be obtained, for example, by a conventional radicalpolymerization or the like of the monomers corresponding with each ofthe structural units, using a radical polymerization initiator such asazobisisobutyronitrile (AIBN).

Further, when the polymer (A″) has a cyclic-main chain structural unit,the polymer (A″) can be synthesized, for example, by a method describedin Japanese Unexamined Patent Application, First Publication No.2006-291177.

[Organic Solvent]

The organic solvent to be blended within the organic film-formingcomposition may be any organic solvent which can dissolve the respectivecomponents to give a uniform solution. For example, one or more kinds ofany organic solvent can be appropriately selected from those which havebeen conventionally known as solvents for a chemically amplified resist.Examples of the organic solvent include lactones such asγ-butyrolactone; ketones such as acetone, methyl ethyl ketone,cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and2-heptanone; polyhydric alcohols, such as ethylene glycol, diethyleneglycol, propylene glycol and dipropylene glycol; compounds having anester bond, such as ethylene glycol monoacetate, diethylene glycolmonoacetate, propylene glycol monoacetate, and dipropylene glycolmonoacetate; polyhydric alcohol derivatives including compounds havingan ether bond, such as a monoalkylether (e.g., monomethylether,monoethylether, monopropylether or monobutylether) or monophenylether ofany of these polyhydric alcohols or compounds having an ester bond(among these, propylene glycol monomethyl ether acetate (PGMEA) andpropylene glycol monomethyl ether (PGME) are preferable); cyclic etherssuch as dioxane; esters such as methyl lactate, ethyl lactate (EL),methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethylpyruvate, methyl methoxypropionate, and ethyl ethoxypropionate; andaromatic organic solvents such as anisole, ethylbenzylether,cresylmethylether, diphenylether, dibenzylether, phenetole,butylphenylether, ethylbenzene, diethylbenzene, pentylbenzene,isopropylbenzene, toluene, xylene, cymene and mesitylene.

Alternatively, as the organic solvent to be blended in the organic filmforming composition, an alcohol organic solvent, a fluorine organicsolvent or an ether organic solvent having no hydroxyl group can beused. These organic solvents can be preferably used for an organicfilm-forming composition because these organic solvents hardly dissolvethe resist film formed from the aforementioned resist composition.

The below-described organic solvents can be used individually, or atleast 2 solvents may be mixed together. In terms of coatability andsolubility of materials such as the resin component and the like, analcohol organic solvent is preferable.

The term “alcohol organic solvent” refers to a compound in which atleast one hydrogen atom within an aliphatic hydrocarbon has beensubstituted with a hydroxyl group, and is a liquid at normal temperature(room temperature) and normal pressure (atmospheric pressure). Thestructure of the main chain constituting the aforementioned aliphatichydrocarbon may be a chain-like structure or a cyclic structure, or mayinclude a cyclic structure within the chain-like structure, or mayinclude an ether bond within the chain-like structure.

A “fluorine organic solvent” is a compound containing a fluorine atomand is in the form of a liquid at normal temperature (room temperature)and normal pressure (atmospheric pressure).

An “ether organic solvent having no hydroxyl group” refers to a compoundthat contains an ether bond (C—O—C) within the molecule but has nohydroxyl group, and is in the form of a liquid at normal temperature(room temperature) and normal pressure (atmospheric pressure). The etherorganic solvent having no hydroxyl group is preferably a compound havingneither a hydroxyl group nor a carbonyl group.

As the alcohol organic solvent, a monohydric alcohol, a dihydric alcoholor a dihydric alcohol derivative is preferable.

Although it depends on the number of carbon atoms, as the monohydricalcohol, a primary or secondary alcohol is preferable, and a primarymonohydric alcohol is particularly desirable.

The term “monohydric alcohol” refers to a compound in which ahydrocarbon compound composed of only carbon and hydrogen has onehydrogen atom substituted with a hydroxy group, and does not includepolyhydric alcohol derivatives having two or more hydroxy groups. Thehydrocarbon compound may have a chain-like structure or a ringstructure.

The term “dihydric alcohol” refers to a compound in which theaforementioned hydrocarbon compound has two hydrogen atoms substitutedwith hydroxy groups, and does not include polyhydric alcohol derivativeshaving three or more hydroxy groups.

Examples of the dihydric alcohol derivative include compounds in which adihydric alcohol has one hydroxy group substituted with a substituent(e.g., alkoxy group, alkoxyalkyloxy group or the like).

The boiling point of the alcohol organic solvent is preferably 80 to160° C., and more preferably 90 to 150° C. In terms of coatability,stability of the composition during storage and the heat temperature,the boiling point is most preferably 100 to 135° C.

Specific examples of the alcohol organic solvent having a chain-likestructure include propylene glycol (PG), 1-butoxy-2-propanol (PG),n-hexanol, 2-heptanol, 3-heptanol, 1-heptanol, 5-methyl-1-hexanol,6-methyl-2-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol,2-ethyl-1-hexanol, 2-(2-butoxyethoxy)ethanol, n-pentylalcohol,s-pentylalcohol, t-pentylalcohol, isopentylalcohol, isobutanol (alsoreferred to as isobutylalcohol or 2-methyl-1-propanol),isopropylalcohol, 2-ethylbutanol, neopentylalcohol, n-butanol,s-butanol, t-butanol, 1-propanol, 2-methyl-1-butanol, 2-methyl-2-butanoland 4-methyl-2-pentanol.

Further, specific examples of those having a ring structure includecyclopentane methanol, 1-cyclopentylethanol, cyclohexanol, cyclohexanemethanol (CM), cyclohexane ethanol, 1,2,3,6-tetrahydrobenzyl alcohol,exo-norborneol, 2-methylcyclohexanol, cycloheptanol,3,5-dimethylcyclohexanol, and benzyl alcohol.

Among alcohol organic solvents, a monohydric alcohol or a dihydricalcohol derivative having a chain-like structure is preferable,1-butoxy-2-propanol (BP), isobutanol (2-methyl-1-propanol),4-methyl-2-pentanol or n-butanol is more preferable, and isobutanol(2-methyl-1-propanol) or 1-butoxy-2-propanol (BP) is most preferable.

As an example of a fluorine organic solvent,perfluoro-2-butyltetrahydrofuran can be given.

Preferable examples of the ether organic solvent having no hydroxylgroup include compounds represented by general formula (s-1) shownbelow.

R⁴⁰—O—R⁴¹  (s-1)

In the formula, each of R⁴⁰ and R⁴¹ independently represents amonovalent hydrocarbon group, provided that R⁴⁰ and R⁴¹ may be mutuallybonded to form a ring. —O— represents an ether bond.

In the aforementioned formula, as the hydrocarbon group for R⁴⁰ and R⁴¹,for example, an alkyl group, an aryl group or the like can be mentioned,and an alkyl group is preferable. It is more preferable that both of R⁴⁰and R⁴¹ represent an alkyl group, and it is particularly desirable thatR⁴⁰ and R⁴¹ represent the same alkyl group.

The alkyl group for R⁴⁰ and R⁴¹ is not particularly limited andincludes, for example, a linear, branched or cyclic alkyl group having 1to 20 carbon atoms. Part or all of the hydrogen atoms of the alkyl groupmay or may not be substituted with halogen atoms or the like.

The alkyl group preferably has 1 to 15 carbon atoms, and more preferably1 to carbon atoms, because the coatability on the resist film becomessatisfactory. Specific examples include an ethyl group, a propyl group,an isopropyl group, an n-butyl group, an isobutyl group, an n-pentylgroup, an isopentyl group, a cyclopentyl group and a hexyl group, and ann-butyl group and an isopentyl group are particularly desirable.

The halogen atom, with which hydrogen atoms of the alkyl group may besubstituted, is preferably a fluorine atom.

The aryl group for R⁴⁰ and R⁴¹ is not particularly limited. For example,an aryl group having 6 to 12 carbon atoms may be used in which part orall of the hydrogen atoms of the aryl group may or may not besubstituted with alkyl groups, alkoxy groups, halogen atoms, or thelike.

The aryl group is preferably an aryl group having 6 to 10 carbon atomsbecause it can be synthesized at a low cost. Specific examples thereofinclude a phenyl group, a benzyl group and a naphthyl group.

The alkyl group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkyl group having 1 to 5 carbon atoms,and more preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkoxy group having 1 to 5 carbon atoms,and more preferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may besubstituted, is preferably a fluorine atom.

Alternatively, in the aforementioned formula, R⁴⁰ and R⁴¹ may bemutually bonded to form a ring.

In this case, R⁴⁰ and R⁴¹ each independently represents a linear orbranched alkylene group (preferably an alkylene group of 1 to 10 carbonatoms) and R⁴⁰ and R⁴¹ are bonded to form a ring. Further, a carbon atomof the alkylene group may be substituted with an oxygen atom.

Specific examples of such ether-based organic solvents include1,8-cineole, tetrahydrofuran and dioxane.

The boiling point (at normal pressure) of the ether organic solventhaving no hydroxyl group is preferably within a range from 30 to 300°C., more preferably from 100 to 200° C., and still more preferably from140 to 180° C. When the boiling point is at least as large as the lowerlimit of the above-mentioned temperature range, the solvent hardlyevaporates during the spin coating process for coating, therebysuppressing coating irregularities and improving the resulting coatingproperties. On the other hand, when the boiling point is no more thanthe upper limit of the above-mentioned temperature range, the solvent issatisfactorily removed from the organic film by a bake treatment,thereby improving formability of the resist film. Further, when theboiling point is within the above-mentioned temperature range, thestability of the composition upon storage is further improved. Theabove-mentioned temperature range for the boiling point of the solventis also preferable from the viewpoints of the heating temperature.

Specific examples of the ether organic solvent having no hydroxyl groupinclude 1,8-cineole (boiling point: 176° C.), dibutyl ether (boilingpoint: 142° C.), diisopentyl ether (boiling point: 171° C.), dioxane(boiling point: 101° C.), anisole (boiling point: 155° C.), ethylbenzylether (boiling point: 189° C.), diphenyl ether (boiling point: 259° C.),dibenzyl ether (boiling point: 297° C.), phenetole (boiling point: 170°C.), butylphenyl ether, tetrahydrofuran (boiling point: 66° C.),ethylpropyl ether (boiling point: 63° C.), diisopropyl ether (boilingpoint: 69° C.), dihexyl ether (boiling point: 226° C.), and dipropylether (boiling point: 91° C.).

The ether organic solvent having no hydroxyl group is preferably acyclic or chain-like, ether-based organic solvent, and more preferablyat least one member selected from the group consisting of 1,8-cineole,dibutyl ether and diisopentyl ether.

The amount of the organic solvent to be blended within the organicfilm-forming composition is not particularly limited, and isappropriately adjusted to a concentration which enables coating on theresist film. For example, when an organic film-forming compositioncontaining an acid or an acid generator component, a resin and anorganic solvent is used, the organic solvent is used in an amount suchthat the resin concentration becomes preferably from 0.2 to 10% byweight, and more preferably from 1 to 5% by weight.

If desired, the organic film-forming composition may have a surfactant,a sensitizer, a cross-linking agent, a halation prevention agent, astorage stabilizer, a colorant, a plasticizer, an antifoaming agent, orthe like added thereto.

Examples of the surfactant include nonionic surfactants, anionicsurfactants, cationic surfactants, amphoteric surfactants, siliconesurfactants, polyalkylene oxide-based surfactants, andfluorine-containing surfactants. When a surfactant is used, the amountof the surfactant relative to 100 parts by weight of the resin ispreferably 0.01 to 0.5 part by weight, and more preferably 0.02 to 0.1part by weight.

According to the method of forming a resist pattern of the presentinvention, a negative-tone resist pattern having an excellent shape canbe formed with a high resolution by a developing process in which achemically amplified resist composition conventionally known as apositive type is used in combination with an alkali developing solution.

Further, according to the method of forming a resist pattern of thepresent invention, the resolution becomes excellent in a resist pattern(such as an isolated trench pattern, an extremely small, dense contacthole pattern, or the like) having a region where the optical strengthbecomes weak (region where irradiation by exposure is not satisfactorilyreached) is likely to be generated in a film thickness direction.

Further, by the method of forming a resist pattern according to thepresent invention, it is possible to form a highly densed resistpattern. For example, it becomes possible to form a contact hole patternin which each of the holes are close to each other with excellentdimension uniformity with no fluctuation of dimension, e.g., thedistance between the holes is about 30 to 50 nm.

Furthermore, the method of forming a resist pattern according to thepresent invention can be performed by existing exposure apparatuses andexisting facilities.

Moreover, by using a double exposure method in the method of forming aresist pattern according to the present invention, the number of stepscan be reduced as compared to a double patterning in which each of alithography step and a patterning step are performed at least twice.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

<Production of Resist Composition>

Examples 1 to 5, Comparative Example 1

The components shown in Table 1 were mixed together and dissolved toobtain resist compositions.

TABLE 1 Resist Compo- Compo- Compo- Compo- Compo- Compo- compo- nentnent nent nent nent nent sition (A) (C) (Z) (D) (F) (S) Ex. 1 (A)-1(C)-1 (G)-1 (D)-1 (F)-1 (S)-1 [100] [10.0]  [10.0] [4.0] [3.0] [3000]Ex. 2 (A)-1 (C)-2 (G)-1 (D)-1 (F)-1 (S)-1 [100] [12.3]  [10.0] [4.0][3.0] [3000] Comp. (A)-1 (C)-3 (G)-1 (D)-1 (F)-1 (S)-1 Ex. 1 [100][15.1]  [10.0] [4.0] [3.0] [3000] Ex. 3 (A)-1 (C)-4 (G)-1 (D)-1 (F)-1(S)-1 [100] [6.3] [10.0] [4.0] [3.0] [3000] Ex. 4 (A)-1 (C)-5 (G)-1(D)-1 (F)-1 (S)-1 [100] [11.0]  [10.0] [4.0] [3.0] [3000] Ex. 5 (A)-1(C)-6 (G)-1 (D)-1 (F)-1 (S)-1 [100] [11.1]  [10.0] [4.0] [3.0] [3000]

In Table 1, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added, and the reference charactersindicate the following.

(A)-1: a copolymer represented by chemical formula (A1-1) shown below.Mw: 7,000, Mw/Mn: 1.70. In the chemical formula, the subscript numeralsshown on the bottom right of the parentheses ( ) indicate the proportion(molar ratio) of the respective structural units, and 1/m=50/50.

(C)-1 to (C)-6: compounds represented by chemical formulae (C)-1 to(C)-6 shown below, respectively.

(G)-1: a compound represented by chemical formula (G)-1 shown below.

(D)-1: heptafluorobutylamine (CF₃CF₂CF₂CH₂NH₂, boiling point=69° C.,pKa=5.6).

(F)-1: a polymer represented by chemical formula (F)-1 shown below. Mw:24,000, Mw/Mn: 1.38. In the chemical formula, the subscript numeralsshown on the bottom right of the parentheses ( ) indicate the proportion(molar ratio) of the respective structural units.

(S)-1: a mixed solvent of propylene glycol monomethyl etheracetate/propylene glycol monomethyl ether=6/4 (weight ratio).

<Formation of Resist Pattern>

Step (1)

An organic antireflection film composition (product name: ARC95,manufactured by Brewer Science Ltd.) was applied to a 12-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicantireflection film having a thickness of 90 nm.

Then, a resist composition of Example or Comparative Example wasspin-coated on the organic antireflection film, thereby forming a resistfilm having a film thickness of 100 nm. Thereafter, without conductingprebaking (PAB) of the thus formed resist film, the substrate wasallowed to stand on a cooling plate at 23° C. for 60 seconds.

Step (2)

Subsequently, the resist film was irradiated with an ArF excimer laser(193 nm) through a mask (6% half tone) targeting a contact hole pattern(CH pattern) with a hole diameter of 60 nm and a pitch of 120 nm, usingan ArF exposure apparatus NSR-S609B (manufactured by Nikon Corporation;NA (numerical aperture)=1.07, Crosspole (0.78/0.97) w/POLANO).

Step (3)

Next, a baking treatment (PEB: post exposure bake) was conducted at 90°C. for 60 seconds.

Step (4)

Thereafter, alkali developing was conducted for 20 seconds at 23° C. ina 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co.,Ltd.).

[In-Plane Uniformity (CDU) of Pattern Size]

With respect to each CH pattern having the above target size obtained inthe [Formation of resist pattern], 100 holes in the CH pattern wasobserved from the upper side thereof using a measuring scanning electronmicroscope (SEM) (product name: S-9380, manufactured by HitachiHigh-Technologies Corporation; acceleration voltage: 300V), and the holediameter (nm) of each hole was measured. From the results, the value of3 times the standard deviation σ (i.e., 3σ) was determined. The resultsare indicated “CDU” in Table 2.

The smaller the thus determined 3σ value is, the higher the level of thedimension uniformity (CD uniformity) of the plurality of holes formed inthe resist film.

TABLE 2 Comp. Ex. 1 Ex. 2 Ex. 1 Ex. 3 Ex. 4 Ex. 5 CDU 11.4 nm 12.2 nm17.2 nm 14.0 nm 10.0 nm 11.4 nm (3σ)

From the results shown in Table 2, it can be confirmed that the resistcompositions of Examples 1 to 5 exhibited excellent dimension uniformityas compared to the resist composition of Comparative Example 1, and werecapable of forming a negative-tone resist pattern having an excellentshape with a high resolution.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resist composition comprising a base component(A) that exhibits increased solubility in an alkali developing solutionand a photobase generator component (C) that generates base uponexposure, the resist composition being used in a method of forming aresist pattern comprising: a step (1) in which the resist composition isapplied to a substrate to form a resist film; a step (2) in which theresist film is subjected to exposure; a step (3) in which baking isconducted after the step (2), such that, at an exposed portion of theresist film, the base generated from the photobase generator component(C) upon the exposure and an acid provided to the resist film in advanceare neutralized, and at an unexposed portion of the resist film, thesolubility of the base component (A) in an alkali developing solution isincreased by the action of the acid provided to the resist film inadvance; and a step (4) in which the resist film is subjected to analkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved, wherein the photobase generator component (C) comprises acompound represented by general formula (C1) shown below:

wherein R¹ represents a group which forms an aromatic ring together withthe two carbon atoms bonded to the R¹ group, provided that the aromaticring may have a nitro group or a substituent other than the nitro groupbonded to the aromatic ring; R² represents a hydrogen atom or ahydrocarbon group which may have a substituent; and R³ represents ahydrogen atom, a carboxy group or a hydrocarbon group of 1 to 15 carbonatoms which may have a substituent, provided that part of the carbonatoms constituting the hydrocarbon group for R³ may be replaced with ahetero atom.
 2. The resist composition according to claim 1, whichfurther comprises an acidic compound component or an acid generatorcomponent.
 3. A method of forming a resist pattern, comprising: a step(1) in which a resist composition comprising a base component (A) thatexhibits increased solubility in an alkali developing solution and aphotobase generator component (C) that generates a base upon exposureand contains a compound represented by general formula (C1) shown belowis applied to a substrate to form a resist film; a step (2) in which theresist film is subjected to exposure; a step (3) in which baking isconducted after the step (2), such that, at an exposed portion of theresist film, the base generated from the photobase generator component(C) upon the exposure and an acid provided to the resist film in advanceare neutralized, and at an unexposed portion of the resist film, thesolubility of the base component (A) in an alkali developing solution isincreased by the action of the acid provided to the resist film inadvance; and a step (4) in which the resist film is subjected to analkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved:

wherein R¹ represents a group which forms an aromatic ring together withthe two carbon atoms bonded to the R¹ group, provided that the aromaticring may have a nitro group or a substituent other than the nitro groupbonded to the aromatic ring; R² represents a hydrogen atom or ahydrocarbon group which may have a substituent; and R³ represents ahydrogen atom, a carboxy group or a hydrocarbon group of 1 to 15 carbonatoms which may have a substituent, provided that part of the carbonatoms constituting the hydrocarbon group for R³ may be replaced with ahetero atom.
 4. The method of forming a resist pattern according toclaim 3, wherein the resist composition further comprises an acidiccompound component or an acid generator component.
 5. The method offorming a resist pattern according to claim 4, wherein the basegenerated from the photobase generator component (C) upon exposure isneutralized in the step (2).